Newline spacing issues in Latex Overleaf

Question

so i will attach an image to show my issue, and also show the preamble.tex, styles.sty, and main document coee. So my issue is that i don't know exactly what to do, such there is a margin/space between the Abstract and the "body text".

Also if anyone would be so kind to tell me how i can change Font sizes of the body text and the spacing vertically in the body text i would really appreciate that. I a bit new to overleaf Latex, so kindly suggest your ideas in detail if possible such that i can try your solutions on my end.

Preamble.tex

\usepackage[a4paper,textwidth=18cm,textheight=24cm,top=2.85cm, bottom=2.85cm, left=1.5cm, right=1.5cm]{geometry}
\usepackage{meta/styles}
\usepackage[utf8]{inputenc}
\usepackage{xcolor}
\usepackage{hyperref} 
\hypersetup{backref=true,       
    pagebackref=true,               
    hyperindex=true,                
    colorlinks=true,                
    breaklinks=true,                
    urlcolor= black,                
    linkcolor= blue,                
    bookmarks=true,                 
    bookmarksopen=false,
    filecolor=black,
    citecolor=blue,
    linkbordercolor=blue
}

\usepackage{lmodern}
\usepackage{graphicx}
\usepackage[export]{adjustbox}
\usepackage{times}
\usepackage{apacite}
\usepackage{fancyhdr}
\usepackage{lastpage}
\usepackage[normalem]{ulem}
\useunder{\uline}{\ul}{}
\usepackage[danish]{babel}
\usepackage[figurename=Figur]{caption}


% left justified caption
\makeatletter
\long\def\@makecaption#1#2{%
\vskip\abovecaptionskip
\sbox\@tempboxa{#1. #2}%
\ifdim \wd\@tempboxa >\hsize
#1. #2\par
\else
\global \@minipagefalse
\hb@xt@\hsize{\box\@tempboxa\hfil}%
\fi
\vskip\belowcaptionskip}
\makeatother

Main document.

\documentclass[10pt]{article}
\input{meta/preamble.tex}
\usepackage{natbib}
\setcitestyle{numbers}
\setcitestyle{square}
\begin{document}
\noindent

\bibliographystyle{apacite}
\title{TITEL}

\twocolumn[
\begin{@twocolumnfalse}
\maketitle
\abstract
\input{sektioner/Introduktion/Abstract}
\keywords
Keyword 1 - Keyword2 - Keyword3
\end{@twocolumnfalse}
]

\newpage

\input{sektioner/Introduktion/Introduktion}
\input{sektioner/Metode/Metode}
\input{sektioner/Metode/Metodisk fremgangsmåde}

\newpage
\bibliography{bibliography}
\end{document}

Styles.sty

\setlength\columnsep{0.4cm}
\newlength\titlebox
\setlength\titlebox{4.9cm}

\flushbottom \twocolumn \sloppy %

\def\addcontentsline#1#2#3{}

\def\maketitle{\par
 \begingroup
 \def\thefootnote{\fnsymbol{footnote}}
 \def\@makefnmark{\hbox to 0pt{$^{\@thefnmark}$\hss}}
 \if@twocolumn
   \twocolumn[\@maketitle]
 \else
   \global\@topnum\z@
   \@maketitle
 \fi
 \@thanks
 \endgroup
 \setcounter{footnote}{0}
 \let\maketitle\relax
 \let\@maketitle\relax
 }

\def\authorname#1{\gdef\@authorname{#1}}
\gdef\@authorname{Author}

\def\authoraddr#1{\gdef\@authoraddr{#1}}
\gdef\@authoraddr{Affiliation\\Country\\Contact Details}

\def\secondauthoraddr#1{\def\@secondauthoraddr{#1}}
\secondauthoraddr{}

\def\makesecondauthoraddr{%
    \if \@secondauthoraddr
        %nothing to do if it is not defined
    \else 
          \\
          \large{\@secondauthoraddr}
    \fi
}

\def\@maketitle{
  \begin{center}
    \LARGE{\bf\@title}
    \large
    \vbox{%
    \vskip 0.1in
    \def\And{%
      \end{tabular}\hfil\linebreak[0]\hfil%
      \begin{tabular}[t]{c}\bf\rule{\z@}{24\p@}\ignorespaces%
    }
    \def\AND{%
      \end{tabular}\hfil\linebreak[4]\hfil%
      \begin{tabular}[t]{c}\bf\rule{\z@}{24\p@}\ignorespaces%
    }
    \begin{tabular}[t]{c}\bf\rule{\z@}{24\p@}\@author\end{tabular}%
    \vskip 0.3in \@minus 0.1in \center{Vejleder: Kasper Trolle Elmholdt}\\
    \vskip 0.1in \@minus 0.1in \center{\@date}
  }
  \end{center}
  \vskip 2ex
}


\renewcommand{\abstract}{\section*{Abstract}}
\newcommand{\keywords}{\paragraph{Keywords:}}
\newcommand{\acknowledgements}{\section*{Acknowledgements}}


\def\section{\@startsection {section}{1}{\z@}{-3.0ex plus
    -0.5ex minus -.2ex}{1.7ex plus 0.3ex minus .2ex}{\large\bf\raggedright}}
\def\subsection{\@startsection{subsection}{2}{\z@}{-3.0ex plus
    -0.5ex minus -.2ex}{1.7ex plus .2ex}{\normalsize\bf\raggedright}}
\def\subsubsection{\@startsection{subsubsection}{3}{\z@}{-3.0 ex plus
   -0.5ex minus -.2ex}{1.7ex plus .2ex}{\normalsize\bf\raggedright}}
\def\paragraph{\@startsection{paragraph}{4}{\z@}{1.5ex plus
   0.5ex minus .2ex}{-1em}{\normalsize\bf}}
\def\subparagraph{\@startsection{subparagraph}{5}{\parindent}{1.5ex plus
   0.5ex minus .2ex}{-1em}{\normalsize\bf}}

\def\@normalsize{\@setsize\normalsize{10pt}\xpt\@xpt}
\def\small{\@setsize\small{9pt}\ixpt\@ixpt}
\def\footnotesize{\@setsize\footnotesize{9pt}\ixpt\@ixpt}
\def\scriptsize{\@setsize\scriptsize{8pt}\viipt\@viipt}
\def\tiny{\@setsize\tiny{7pt}\vipt\@vipt}
\def\large{\@setsize\large{12pt}\xiipt\@xiipt}
\def\Large{\@setsize\Large{14pt}\xivpt\@xivpt}
\def\LARGE{\@setsize\LARGE{18pt}\xviipt\@xviipt}
\def\huge{\@setsize\huge{23pt}\xxpt\@xxpt}
\def\Huge{\@setsize\Huge{28pt}\xxvpt\@xxvpt}

\renewcommand{\figurename}{Figur}

Answer 1

So the solution was to ad vspace:

\keywords Keyword 1 - Keyword2 - Keyword3 \vspace{12pt} % Adjust the space as needed