\documentclass[titlepage]{lecture}

\usepackage{standalone}
\usepackage{tikz}
\usepackage{subcaption}

\title{Analysis II}
\author{Prof. Dr. Ekaterina Kostina}
\date{SoSe 2020}

\begin{document}

\newgeometry{right=15mm, left=15mm}
\maketitle
\restoregeometry

\tableofcontents

\input{ana1.tex}
\input{ana2.tex}
\input{ana3.tex}
\input{ana4.tex}
\input{ana5.tex}
\input{ana6.tex}
\input{ana7.tex}
\input{ana8.tex}
\input{ana9.tex}
\input{ana10.tex}
\input{ana11.tex}
\input{ana12.tex}

\end{document}