Update on Overleaf.

litis-demo.tex

@@ -16,7 +16,7 @@
 
 % Use starred version (e.g. \section*{Section name}) 
 % to disable (sub)section page.
-\section{Section 1}
+\section{Section A B C D E F G F H I J K L M N O P}
 \subsection{Subsection 1.1}
 \begin{frame}{Simple frame}
     This is a simple frame.

theme/beamerinnerthemelitis.sty

@@ -176,14 +176,14 @@
     }
 
     \vspace{-2.5\baselineskip}
-    \begin{minipage}[b][0.45\paperheight]{\textwidth}
+    \begin{minipage}[b][0.45\paperheight]{0.66\textwidth}
         \usebeamerfont{sectiontitle}
         \usebeamercolor[fg]{sectiontitle}
         \let\hyperlink\@secondoftwo\insertsection
     \end{minipage}
 
     \vspace{\baselineskip}
-    \begin{minipage}[t][0.5\paperheight]{\textwidth}
+    \begin{minipage}[t][0.5\paperheight]{0.66\textwidth}
         \usebeamerfont{subsectiontitle}
         \usebeamercolor[bg]{sectiontitle}
         \insertsubsection