%Kopf und Fußzeile
\usepackage[headsepline,
] 
{scrlayer-scrpage} 
\clearpairofpagestyles
\lohead{
\newline UNIVERSITÄT
\newline Institut für XXX
\newline MODULNAME - SEM
\newline DOZENT
}
\rohead{
\newline REFERENT
\newline XX.XX.XXXX
}
%\cfoot{\pagemark}

\documentclass[paper=A4,11pt]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[left=2cm,right=2cm,top=0.56cm,bottom=2cm,head=69pt,includeheadfoot]{geometry}

\usepackage{graphicx}

%Kopf und Fußzeile
\usepackage[headsepline,footsepline
] 
{scrlayer-scrpage} 
\clearpairofpagestyles
\lohead{
\newline Uni
\newline Institut für XXX
\newline MODULNAME - TRIM
\newline Dozent
}
\rohead{
\newline REFERENT
\newline XX.XX.XXXX
}
\cfoot{\pagemark}


\begin{document}
%Metadaten
bla
\end{document}

[25]
! Extra }, or forgotten $.
<recently read> }
                 
l.4 
    
? 
! Missing } inserted.
<inserted text> 
                }
l.4 
    
? 

\documentclass[framenumber]{beamer}
\usepackage{fancybox}
\begin{document}
	\begin{frame}
		\begin{itemize}
			\item BLA
			\item BLA
			\item BLA
			\item BLA
			 \begin{ovalbox}
					$BLA!=\pi!$ $\longleftarrow$ BLABLABLA
				\end{ovalbox}
		\end{itemize}
	\end{frame}	
\end{document}

\documentclass[framenumber]{beamer}
\usepackage{tcolorbox} %Für alle nur denkbaren Frames
\newtcbox{\mybox}{colback=green!5!white,
	colframe=green!75!black}
\begin{document}
	\begin{frame}
		\begin{itemize}
			\item BLA
			\item BLA
			\item BLA
			\item BLA
			 \mybox{$\longleftarrow$ BLABLABLA
				}
		\end{itemize}
	\end{frame}	
\end{document}

\newtcbox{\mybox}{colback=green!5!white,
	colframe=green!75!black, box align = center}

\resizebox{\linewidth}{!}{$$ \eta = \eta_{\text{Schwarzschild}} \times { e^{\phi_H} \over 1-8\pi G_\text{N}\rho_H r_H^2/c^4}, \quad \phi_\text{H} = {4\pi G_N\over c^4} \; \int_{r_\text{H}}^\infty {(\rho-p_r) \; r \over 1-2m(r)/r} \; \mathrm{d} r \geq 0 $$}