\documentclass{beamer}
\usepackage{etoolbox}
\makeatletter
\patchcmd{\beamer@section}
{\def\insertsectionhead{\hyperlink{Navigation\the\c@page}{#1}}}
{\edef\insertsectionhead{\noexpand\hyperlink{Navigation\the\c@page}{#1}}}
{}{}
\patchcmd{\beamer@subsection}
{\def\insertsubsectionhead{\hyperlink{Navigation\the\c@page}{#1}}}
{\edef\insertsubsectionhead{\noexpand\hyperlink{Navigation\the\c@page}{#1}}}
{}{}
\makeatother
\usetheme{AnnArbor}
\begin{document}
\section{\texorpdfstring{$\operatorname{e}$-Funktion}{e-Funktion}}
\begin{frame}{$\operatorname{e}$-Funktion}
$\operatorname{e}$-Funktion
\end{frame}
\subsection{Subsection 1}
\begin{frame}{Subsection 1}
Subsection 1 Frame 1
\end{frame}
\begin{frame}{Subsection 1}
Subsection 1 Frame 2
\end{frame}
\end{document}
\usepackage{etoolbox}
\makeatletter
\patchcmd{\beamer@section}
{\def\insertsectionhead{\hyperlink{Navigation\the\c@page}{#1}}}
{\protected@edef\insertsectionhead{\noexpand\hyperlink{Navigation\the\c@page}{#1}}}
{}{}
\patchcmd{\beamer@subsection}
{\def\insertsubsectionhead{\hyperlink{Navigation\the\c@page}{#1}}}
{\protected@edef\insertsubsectionhead{\noexpand\hyperlink{Navigation\the\c@page}{#1}}}
{}{}
\makeatother