\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{matrix,shapes,fit,tikzmark,calc}
\makeatletter
% Foliennummern einfügen (frames nummeriert, nicht slides)
% Insert page numbers (frames numbered, not slides)
\setbeamertemplate{footline}{%
\hfill
\insertframenumber{}/
\inserttotalframenumber
}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
% Idee gefunden unter:
% Idea found at:
% https://tex.stackexchange.com/a/265821
% Markierungen hinzufügen
% Add markers
\addtobeamertemplate{background}{}{\tikzmarkhookinbeamerbackground}
\def\tikzmarkhookinbeamerbackground{}
\def\tikzbackgroundpath#1;{
    \gdef\tikzmarkhookinbeamerbackground{
        \gdef\tikzmarkhookinbeamerbackground{}
        \tikz[remember picture,overlay]\path#1;
    }
}
\tikzset{   
        every picture/.style={remember picture,baseline},
        every node/.style={anchor=base,align=center,outer sep=1.5pt},
        every path/.style={thick},
        }
\begin{frame}
\frametitle{Table markers with tikz}
% Tabelle mit Positionen für Markierungen
% Table with positions for markers
\begin{table}[]
\begin{tabular}{c c c c}
A  & B  & C  & D  \\
\hline
\tikzmark{a11}16 & \tikzmark{a12}3  & \tikzmark{a13}2  & \tikzmark{a14}13 \\
\tikzmark{a21}5  & \tikzmark{a22}10 & \tikzmark{a23}11 & \tikzmark{a24}8  \\
\tikzmark{a31}9  & \tikzmark{a32}6  & \tikzmark{a33}7  & \tikzmark{a34}12 \\
\tikzmark{a41}4  & \tikzmark{a42}15 & \tikzmark{a43}14 & \tikzmark{a44}1
\end{tabular}
\end{table}
% Markierungen der einzelnen slides
% Markings on individual slides
\only<1>{
    \tikzbackgroundpath
        node at ([yshift=-60]current page.center){no markers here};
}
\only<5>{
    \tikzbackgroundpath
        node at ([yshift=-60]current page.center){no markers here};
}
% slide 2 oberes linkes Viertel
% slide 2 upper left quarter
\only<2>{
    \tikzbackgroundpath
        node[rounded corners,line width=1,draw,fill=yellow!20,fit={([yshift=6]pic cs:a11)([xshift=11]pic cs:a22)}]{}
        node at ([yshift=-60]current page.center){upper left quarter};
}
% slide 3 erste Zeile, erste Spalte
% slide 3 first row, first column
\only<3>{
    \tikzbackgroundpath
        node[rounded corners,line width=1,draw,fill=green!20,fit={([yshift=6]pic cs:a11)([xshift=11]pic cs:a11)}]{}
        node at ([yshift=-60]current page.center){first row, first column};
}
% slide 4 bunte Kreise hinter einzelnen Elementen
% slide 4 colored circles behind individual elements
\only<4>{
    \tikzbackgroundpath
         node[circle,
         line width=1,
         %draw,
         fill=red!20,
         fit={([yshift=4,xshift=5.5]pic cs:a11)},
         minimum size=0.5cm]{}
         node[circle,
         line width=1,
         %draw,
         fill=blue!20,
         fit={([yshift=4,xshift=6]pic cs:a22)},
         minimum size=0.5cm]{}
         node at ([yshift=-60]current page.center){colored circles behind individual elements};
}
% slide 6 unteres rechtes Viertel
% slide 6 lower right quarter
\only<6>{
    \tikzbackgroundpath
        node[rounded corners,line width=1,draw,fill=violet!20,fit={([yshift=6]pic cs:a33)([xshift=6]pic cs:a44)}]{}
        node at ([yshift=-60]current page.center){lower right quarter};
}
\end{frame}
%~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\end{document}