A lot of space at the beginning of the page in Latex

Question

There is a lot of space in the beginning which I do no like. And also to other sections (but only the start page of the section). Do you guys have any clue on how to reduce the vertical space between the header and the actual content.

\documentclass[12pt, a4paper, oneside, openany]{scrbook}
\pagestyle{headings}

%page layout
\setlength{\voffset}{0mm}
\setlength{\topmargin}{0mm}
\setlength{\headsep}{0mm}
\setlength{\oddsidemargin}{0mm}
\setlength{\evensidemargin}{0mm}
\setlength{\textheight}{210mm}
\setlength{\textwidth}{150mm}
\setlength{\marginparwidth}{5mm}
\setlength{\marginparsep}{3mm}
\setlength{\marginparpush}{7mm}
\setlength{\parindent}{5mm}
\setlength{\footskip}{0mm}


\usepackage{fontspec}
\fontspec{Times New Roman}
\usepackage{url}
\linespread{1.5}
\usepackage[acronym]{glossaries}
\parindent 10mm
\parskip 5mm
\usepackage{graphicx}
\graphicspath{{images/}}
\usepackage[a4paper]{geometry}

Answer 1

You can redeclare the sectioning command which you'd like to change and set whatever beforeskip you like:

% !TeX TS-program = lualatex

\documentclass[12pt, a4paper, oneside, openany]{scrbook}
\pagestyle{headings}


\RedeclareSectionCommand[beforeskip=0pt]{chapter}

%page layout
\setlength{\voffset}{0mm}
\setlength{\topmargin}{0mm}
\setlength{\headsep}{0mm}
\setlength{\oddsidemargin}{0mm}
\setlength{\evensidemargin}{0mm}
\setlength{\textheight}{210mm}
\setlength{\textwidth}{150mm}
\setlength{\marginparwidth}{5mm}
\setlength{\marginparsep}{3mm}
\setlength{\marginparpush}{7mm}
\setlength{\parindent}{5mm}
\setlength{\footskip}{0mm}


\usepackage{fontspec}
\fontspec{Times New Roman}
\usepackage{url}
\linespread{1.5}
\usepackage[acronym]{glossaries}
\parindent 10mm
\parskip 5mm
\usepackage{graphicx}
\graphicspath{{images/}}
\usepackage[a4paper]{geometry}

\begin{document}

\chapter{title}


\end{document}