I am not sure whether the following example achieves all your goals,
but maybe it helps to get you closer:
- Christoph
\documentclass[]{beamer}
\usepackage[T1]{fontenc}
\usepackage[german]{babel}
\usetheme{Boadilla}
\AtBeginSection[] {
\begin{frame}[plain]
\frametitle{Übersicht}
\tableofcontents[currentsection]
\end{frame}
\addtocounter{framenumber}{-1}
}
\AtBeginSubsection[] {
\begin{frame}[plain]
\frametitle{Übersicht}
\tableofcontents[currentsubsection]
\addtocounter{framenumber}{-1}
\end{frame}
}
\begin{document}
\section{A}
\subsection{aa}
\begin{frame}bla1\end{frame}
\section{B}\subsection{bb}\begin{frame}bla2\end{frame}
\begin{frame}bla3\end{frame}
\section{C}\subsection{cc}\begin{frame}bla4\end{frame}
\end{document}