\documentclass[11pt]{beamer}
\usetheme{Madrid}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}

\author[Tronto]{Sebastiano Tronto}
\title[Example]{Example presentation}

\newtheorem{prop}{Proposition}

\setbeamercovered{transparent} 
\setbeamertemplate{navigation symbols}{} 
\logo{\includegraphics[scale=0.05]{unilu.jpg}} 

%\date{} 


\begin{document}

\begin{frame}
\titlepage
\end{frame}

%\begin{frame}
%\tableofcontents
%\end{frame}

\section[this]{This is the first section}

\begin{frame}{Frame number one}
\uncover<2->{
\begin{align*}
	\sum_{i=1}^n\frac{i}{2}
\end{align*}
}

\begin{itemize}[<+->]
\item One item
\item another random things
\item third line
\item fourth element
\end{itemize}
\end{frame}

\begin{frame}{A second frame}
\begin{theorem}
A theorem
\end{theorem}

{

\setbeamercolor{block body}{fg=red,bg=gray}
\begin{prop}
My proposition
\end{prop}
}

\begin{block}{Title of the block}
this is my custom block
\end{block}

\end{frame}

\begin{frame}{Columns}
\begin{columns}
	\column{0.5\textwidth}
		\begin{itemize}[<+->]
			\item One item
			\item another random things
			\item third line
			\item fourth element
		\end{itemize}
	
	\column{0.2\textwidth}
		hello
	
	\column{0.3\textwidth}
		\includegraphics[scale=0.1]{unilu.jpg}
\end{columns}
\end{frame}

\end{document}