I noticed that my titlepage is not vertically centered. I tried \vfill, \vspace{\fill}, \vspace*, and \usepackage{titling}.
\documentclass[12pt, oneside]{article}
\usepackage{graphicx}
\usepackage{geometry}
\geometry{a4paper}
\usepackage{float}
\usepackage[american]{babel}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage[onehalfspacing]{setspace}
\begin{document}
\begin{titlepage}
\begin{center}
\begin{huge}
name of university \\
\end{huge}
\begin{figure}[H]
\centering
\includegraphics[width=0.5\textwidth]{Unilogo}
\end{figure}
\vspace{1cm}
{\Large name of institute} \\
\vspace{5mm}
Research focus \textit{research name} \\
Project \textit{project name} \\
\vspace{2cm}
\begin{large}
\textbf{title of thesis} \\
\end{large}
\vspace{5mm}
Master thesis in Biomedical Sciences \\
Submitted on Date \\
\vspace{1cm}
name \\
Matriculation number: \\
\vspace{2.5cm}
\begin{tabular}{rl}
{\bfseries Supervisors} & name and name\\
{\bfseries Examiners} & name and name \\
\end{tabular}
\end{center}
\end{titlepage}
\end{document}

\usepackage[showframe]{geometry}and see that it is almost centered. Are you aware that the (top/bottom) margins are not automatically symmetric? – Dr. Manuel Kuehner May 01 '17 at 17:29geometrydocumentation (https://www.ctan.org/pkg/geometry). Try\usepackage[showframe,margin=10mm]{geometry}as a start so see the effect. – Dr. Manuel Kuehner May 01 '17 at 17:49figure-environment and just use\includegraphics. – Skillmon May 01 '17 at 19:33! Undefined control sequence. l.21 \includegraphics– David Carlisle May 03 '17 at 16:12