how to remove the space between new chapter and the section after

Question

I am writing a report using LATEX where i write each part in its own file and include everything at the end to my main file. My problem is that i am not able to remove the empty space between the chapter's paragraph and the first section. The same problem occur between the last section from previous chapter and the new chapter. Please find a photo below. my code at main file

\documentclass{report}
\usepackage{graphicx,wrapfig,lipsum}
\usepackage{amsmath}
\usepackage{lipsum}
\usepackage{subcaption}
\usepackage{titlesec}
\usepackage{geometry}
\newgeometry{
top=0.75in,
bottom=0.75in,
outer=0.75in,
inner=1.5in,
}
\title{Variations of rainfall intensity and accumulation depending on elevation in Eidfjord, and investigations of the primary cause behind these variations if existed.}
\author{Zuhir. A Jamaleh}
\date{GEOF232}
\titlespacing*{\chapter}{0pt}{-2cm}{2\baselineskip}
\begin{document}
\maketitle
\section*{Abstract}
%introduction {a short intro, background theory, expected outcome}
\include{introduction}
\include{Background theory}
\include{expectedresult}
%methodology{intro about inst used and locations of stantions, calibration process}
\include{Methodology}
\include{insused}
\include{calic}
%results{}
%discussion 
%conclusion 
%litterature
\bibliographystyle{apalike}
\bibliography{ref}
\end{document}

I have tried to add this code to my main file befor \begin{document} and it did not work. I tried to add it inside the code between the chapter and the following section but it did not work either

\titlespacing*{\chapter}{0pt}{-2cm}{2\baselineskip}

i tried also this one

\documentclass{report}
\usepackage{graphicx,wrapfig,lipsum}
\usepackage{amsmath}
\usepackage{lipsum}
\usepackage{subcaption}
\usepackage{titlesec}
\usepackage{geometry}
\newgeometry{
top=0.75in,
bottom=0.75in,
outer=0.75in,
inner=1.5in,
}
\title{Variations of rainfall intensity and accumulation depending on elevation in Eidfjord, and investigations of the primary cause behind these variations if existed.}
\author{Zuhir. A Jamaleh}
\date{GEOF232}
\titlespacing*{\chapter}{0pt}{0pt}{40pt}
\begin{document}
\maketitle
\section*{Abstract}
%introduction {a short intro, background theory, expected outcome}
\include{introduction}
\include{Background theory}
\include{expectedresult}
%methodology{intro about inst used and locations of stantions, calibration process}
\include{Methodology}
\titlespacing*{\chapter}{0pt}{50pt}{40pt}
\include{insused}
\include{calic}
%results{}
%discussion 
%conclusion 
%litterature
\bibliographystyle{apalike}
\bibliography{ref}
\end{document}