I have the following MWE:
\documentclass[xcolor=pdftex,t,11pt]{beamer}
\AtBeginSection[]
{
\setbeamercolor{section in toc}{fg=alerted text.fg}
\setbeamercolor{section in toc shaded}{fg=structure}
\begin{frame}<beamer>
\frametitle{Outline}
\vspace{-4ex}
\begin{columns}
\begin{column}{.60\textwidth}
\tableofcontents[sections={1-12}, currentsection, hideothersubsections]
\end{column}
\begin{column}{.40\textwidth}
\tableofcontents[sections={13-30}, currentsection, hideothersubsections]
\end{column}
\end{columns}
\end{frame}
}
\newenvironment{stepenumerate}{\begin{enumerate}[<+->]}{\end{enumerate}}
\newenvironment{stepitemize}{\begin{itemize}[<+->]}{\end{itemize} }
\newenvironment{stepenumeratewithalert}{\begin{enumerate}[<+-| alert@+>]}{\end{enumerate}}
\newenvironment{stepitemizewithalert}{\begin{itemize}[<+-| alert@+>]}{\end{itemize} }
\newenvironment{exe}[1][]{\par\medskip
\noindent \textbf{Esempio: }}{\medskip}
\usepackage{multicol}
\usepackage{lmodern}
\usepackage{marvosym}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}
\usepackage{hyperref}
\usepackage[font=scriptsize]{caption}
\usepackage{multicol}
\usepackage{xcolor}
\usepackage{booktabs}
\usepackage{array}
\usepackage{upquote}
\usepackage{tikz}
\newcommand{\matr}[1]{\mathbf{#1}}
\setbeamercolor{button}{bg=unime,fg=white}
%%%%%%%%%%%%%%%%%
% PRESENTATION INFO %
%%%%%%%%%%%%%%%%%
\author{XXX}
\title{ABC}
\subtitle{\large{CDE}}
\institute{{\bf COurse} \\ \vspace{2ex} Department \\Uiversity}
\date{January 2018}
\begin{document}
%%%%%%%%%%%%%%%%
% SLIDE DEFINITIONS %
%%%%%%%%%%%%%%%%
\begin{frame}[plain]
\titlepage
\end{frame}
\begin{frame}{Outline}
\frametitle{Outline}
\begin{columns}[t]
\begin{column}{.55\textwidth}
\tableofcontents[sections={1-12}]
\end{column}
\begin{column}{.5\textwidth}
\tableofcontents[sections={13-30}]
\end{column}
\end{columns}
\end{frame}
\addtocontents{toc}{\vskip -0.1cm}
\section{A}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{B}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{C}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{D}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{E}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{F}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{G}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{A}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{H}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{I}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{J}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{A}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{L}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{A}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{K}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{M}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{N}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{O}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{P}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{Q}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{R}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\section{S}
\begin{frame}[fragile]
\frametitle{Introduction}
\vspace{-2ex}
\begin{itemize}
\item A b C
\end{itemize}
\end{frame}
\end{document}
The problem I face is the following. When I show the outline right before each section to make the reader aware about the development of the discussion, the space between titles of sections is really too much. In fact, I cannot show the title of the last sections. Is there any way I can reduce the space between the title of sections in the outline that appears before each section? Thanks in advance
hideothersubsections\usepackage{hyperref}and\usepackage{xcolor}with beamer.\usepackage{multicol}is probably also unnecassary, as beamer has it's own column mechanism.