how avoid the spaces between paragraphs/tables?

As it seems, source of the your problem is wish (requirement) to have resume in one column format but main text in two columns. This is simple to achieved by use of multicol package, but this have consequences with which you faces: multicol doesn't support floats. This you solve with use of H floats placement, which consequences is inserting white space in text, if floats haven't enough space to places on page where it is inserted in text.

What to do? You have three options:

  • manually move your tables in figures in text by trials so, that empty space will vanish
  • Instead of multicols use article with twocolumn option and insert article's title and summary (abstract) on separated one column text to which follows main text in two column format where you can use standard floats with htb placements' options:
\documentclass[a4paper,12pt,twocolumn, spanish]{article}
% preamble

\begin{document}
\onecolumn
\title{ Title}
\author{Alastor\\ UUC}
\date{\null
 }
\maketitle

\section*{Resumen}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text.

\twocolumn
\section{Introducción}
% main text
\end{document}
  • or make (very) dirty trick in twocolumn document: insert your abstract into last maketitle field:
\documentclass[a4paper,12pt,twocolumn, spanish]{article}
%PAQUETES
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage[left=1.5cm,top=1cm,right=1.5cm,bottom=1.5cm]{geometry}
\usepackage[osf]{newtxtext}
\usepackage{textcomp}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{mathtools}
\usepackage{siunitx}
%\usepackage{multicol}
\usepackage[table]{xcolor}
\definecolor{verde}{rgb}{0.55, 0.71, 0.0} %http://latexcolor.com/ para mas colorcitos
\definecolor{verde1}{rgb}{0.0, 0.5, 0.0}
\usepackage{graphicx}
\usepackage{enumerate}
\usepackage{booktabs, makecell}
\usepackage{float}
\usepackage{caption}
\usepackage{subcaption}
\captionsetup[subfigure]{labelformat=simple}
\renewcommand\thesubfigure{(\alph{subfigure})}

\usepackage{lipsum}

\usepackage[colorlinks=true,citecolor=verde1,linkcolor=black,urlcolor=verde1]{hyperref}

\begin{document}
\title{ Title}
\author{Alastor\\ UUC}
\date{\null
    \begin{minipage}{\textwidth}  % <-----------
    \section*{Resumen}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text.
    \end{minipage}
}
\maketitle

\section{Introducción}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text

\section{Implementacion}

text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
\[
    \begin{multlined}[0.9\linewidth]
A(x) = -20\exp\left(-\frac{|x|}{5}\right)\\
        -\exp\left(\cos(2\pi x)\right) + 20 + \exp(1)
    \end{multlined}
\]
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text

\section{Resultados}

text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text

\begin{table}[ht]
    \rowcolors{2}{gray!25}{white}
   \centering
     \begin{tabular}{S[table-format=1.0e1] c
                     S[table-format=1.4]
                     S[table-format=2.0]}
      \toprule
       {S} & {K} & {\makecell{Long. del\\ intervalo}} & {Valuaciones} \\
        \midrule
        1e-1    & 2 & 1.2    & 6\\
        1e-2    & 2 & 0.96   & 9\\
        1e-3    & 2 & 0.768  & 12\\
        1e-4    & 2 & 0.6144 & 15\\
        1e-5    & 2 & 0.9830 & 19\\
        1e-6    & 2 & 0.7864 & 22\\
        1e-7    & 2 & 0.6291 & 25\\
        1e-8    & 2 & 0.5033 & 28\\
        1e-9    & 2 & 0.8053 & 32\\
        1e-10   & 2 & 0.6442 & 35\\
      \specialrule{\heavyrulewidth}{0pt}{\belowrulesep}
    \end{tabular} 
    \caption{Longitud del intervalo con respecto a $s$ en BM con $x=1/2$}
    \label{tab: s}
\end{table}

\begin{table}[ht]
    \rowcolors{2}{gray!25}{white}
   \centering
     \begin{tabular}{S[table-format=1.0e1] 
                     S[table-format=1.1]
                     S[table-format=1.4]
                     S[table-format=2.0]}
      \toprule
       {S} & {K} & {X} & {V} \\
        \midrule
        1e-2    & 2     & 0.96      & 9\\
        1e-2    & 1.9   & 0.7180    & 9\\
        1e-2    & 1.8   & 0.5290    & 9\\
        1e-2    & 1.7   & 0.6517    & 10\\
        1e-2    & 1.6   & 0.4362    & 10\\
        1e-2    & 1.5   & 0.4271    & 11\\
        1e-2    & 1.4   & 0.3541    & 12\\
        1e-2    & 1.3   & 0.3170    & 14\\
        1e-2    & 1.2   & 0.1961    & 16\\
        1e-2    & 1.1   & 0.1167    & 22\\
      \specialrule{\heavyrulewidth}{0pt}{\belowrulesep}
    \end{tabular}
   \caption{Longitud del intervalo con respecto a $k$ en BM con $x=1/2$}
    \label{tab: k}
\end{table}

\subsection*{Fibonacci Search} %\emph{agrega esto}
\lipsum
 \end{document}

In above MWE I made some off-topic changes in tables and equation design.

enter image description here


@Zarko has the right answer in my opinion and should be accepted as it is the right way to go about typesetting documents.

However, if you for some reason must have your document in two columns the way you do, and if you for some reason must use [H] the way you do, there is a way to control the spaces you wish to narrow:

  1. Using the titlesec package one can control the spacing between the section title and the text using the titlespacing\section{} command
  2. One can use the belowcaptionskip length to control how much space there is after a figure.

MWE:

\documentclass[a4paper,12pt,spanish]{article}
%PAQUETES
\usepackage[utf8]{inputenc} % puede ser redundante si tu flujo de trabajo es en utf-8 y usas TeXlive 2018 o más reciente.
\usepackage[T1]{fontenc} 
\usepackage[spanish]{babel}
\usepackage[left=1.5cm,top=1cm,right=1.5cm,bottom=1.5cm]{geometry} 
\usepackage[osf]{newtxtext}
\usepackage{textcomp} 
\usepackage{amsmath}
\usepackage{amssymb} 
\usepackage{amsthm} 
\usepackage{mathtools} 
\usepackage{siunitx}
\usepackage{multicol}
\usepackage[table]{xcolor}
\usepackage{graphicx} 
\usepackage{enumerate}
\usepackage{booktabs}
\usepackage{float}
\usepackage{caption} 
\usepackage{subcaption} 
\usepackage[colorlinks=true,citecolor=verde1,linkcolor=black,urlcolor=verde1]{hyperref}
\captionsetup[subfigure]{labelformat=simple}
\renewcommand\thesubfigure{(\alph{subfigure})}
\definecolor{verde}{rgb}{0.55, 0.71, 0.0} %http://latexcolor.com/ para mas colorcitos
\definecolor{verde1}{rgb}{0.0, 0.5, 0.0}

\usepackage[compact]{titlesec}
\titlespacing\section{0pt}{1pt minus 1pt}{1pt minus 1pt}
\titlespacing\subsection{0pt}{1pt minus 1pt}{1pt minus 1pt}
\setlength{\belowcaptionskip}{-2pt}


\begin{document}    
\title{ Title}
\author{Alastor\\ UUC}
\date{\null}
\maketitle
\begin{multicols*}{2}
    [
    \section*{Resumen}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text .
    ]

    
\section{Introducción}
text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text 
    
\section{Implementacion}

text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text 
\begin{equation*}
A(x)=-20\mathrm{exp}({-\frac{\left|x\right|}{5}})-\mathrm{exp}({\cos\left(2{\pi}x\right)})+20+\mathrm{exp}(1)
\end{equation*}

text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text 

\section{Resultados}

text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text 

\begin{table}[H]
    \rowcolors{2}{gray!25}{white}
    \centering
    \resizebox{0.4\textwidth}{!}{
     \begin{tabular}{ccccc} 
      \toprule
       S & K & Long. del intervalo & Valuaciones \\ [0.5ex] 
        \midrule
        \num{1e-1}& 2& 1.2& 6\\
        \num{1e-2}& 2& 0.96& 9\\
        \num{1e-3}& 2& 0.768& 12\\
        \num{1e-4}& 2& 0.6144& 15\\
        \num{1e-5}& 2& 0.9830& 19\\
        \num{1e-6}& 2& 0.7864& 22\\
        \num{1e-7}& 2& 0.6291& 25\\
        \num{1e-8}& 2& 0.5033& 28\\
        \num{1e-9}& 2& 0.8053& 32\\
        \num{1e-10}& 2& 0.6442& 35\\
      \bottomrule
    \end{tabular} }
    \caption{Longitud del intervalo con respecto a $s$ en BM con $x=1/2$}
    \label{tab: s}
\end{table}

\begin{table}[H]
    \rowcolors{2}{gray!25}{white}
   \centering
    \resizebox{0.4\textwidth}{!}{
     \begin{tabular}{ccccc} 
      \toprule
       S & K & X & V \\ [0.5ex]
        \midrule
        \num{1e-2}& 2& 0.96& 9\\
        \num{1e-2}& 1.9& 0.7180& 9\\
        \num{1e-2}& 1.8& 0.5290& 9\\
        \num{1e-2}& 1.7& 0.6517& 10\\
        \num{1e-2}& 1.6& 0.4362& 10\\
        \num{1e-2}& 1.5& 0.4271& 11\\
        \num{1e-2}& 1.4& 0.3541& 12\\
        \num{1e-2}& 1.3& 0.3170& 14\\
        \num{1e-2}& 1.2& 0.1961& 16\\
        \num{1e-2}& 1.1& 0.1167& 22\\
      \bottomrule
    \end{tabular} } 
    \caption{Longitud del intervalo con respecto a $k$ en BM con $x=1/2$}
    \label{tab: k}
\end{table}

\subsection*{Fibonacci Search} %\emph{agrega esto}

text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text  


 \end{multicols*}
 \end{document} 

enter image description here