My headline collides with my text / chapters.

\documentclass[a4paper, 12pt, oneside, numbers=noenddot,  ngerman]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{amsmath, amssymb, amsthm}
\usepackage{fullpage}
\usepackage{setspace}
\usepackage{booktabs}
\usepackage{multirow}
\usepackage{float}
\usepackage[automark]{scrpage2}
\begin{document}
\clearscrplain
\setlength{\parindent}{0pt}
\pagenumbering{roman}
\singlespacing
\tableofcontents
\newpage
\pagenumbering{arabic}
\setstretch{1.4}
\section{Section1}
\end{document}


If I use

\setlength{\headsep}{0.45in}


The problem ist fixed however my the top margin before any content, in this case the header is too much for my taste.

• Remove the package fullpage. i.e. %\usepackage{fullpage} – Fran Apr 22 '15 at 20:37
• @Fran Thanks! With this I don't even need the \setlength{\headsep}{0.45in} command. @cfr The 0.4pt are for the thickness of the separation line beneath the header. The 0.45in were for the top margin, the values and units were meant that way. – idkfa Apr 22 '15 at 20:42
• @idkfa Sorry. I misread it. Serves me right for trying to do too many things at once! You should ask Fran to write an answer? – cfr Apr 22 '15 at 21:26

\usepackage[in,empty]{fullpage}

\usepackage[cm,headings]{fullpage}

In other case, do not use this package. The geometry package is a more flexible interface to customize the page layout. Note that in KOMA-script documents you can also use the DIV=<value> option for the document class for this purpose.