\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
\begin{document}
\begin{tikzpicture}
	
	% Air in cylinder
	\draw[fill=blue!20,draw=none](1.2,0) rectangle (2,-1);
	\draw[fill=blue!20,draw=none](2,-0.3) rectangle (3,-0.7);

	% Air in main container
	\draw[fill=blue!20,draw=none](3,0.5) rectangle (6,-3);
	% Pump cylinder
	\node[anchor=south] at (1,0){Pumpe};
	\draw[black,thick](0,0)--(2,0);
	\draw[black,thick](0,-1)--(2,-1);
	\draw[black,thick](2,0)--(2,-0.3)--(3,-0.3);
	\draw[black,thick](2,-1)--(2,-0.7)--(3,-0.7);

	% Main container
	\draw[black,thick](3,-0.3)--(3,0.5)--(4.4,0.5);
	\draw[black,thick](4.6,0.5)--(6,0.5);
	\draw[black,thick](3,-0.7)--(3,-3)--(6,-3)--(6,-0.7);
	\draw[black,thick](6,0.5)--(6,-0.3);
	\node[anchor=north] at (4.5,-3.1){Druckbehälter};
	\node[] at (4.5,-1){Ideales Gas};
	\node[] at (4.5,-2){$(p,\;T)$};

	% Piston
	%\draw[thick, -Latex](-1,-0.5)--(-0.1,-0.5);

	\shade[top color = black, bottom color=black!50!white] (1,0) rectangle (1.2,-0.5);
	\shade[bottom color = black, top color=black!50!white] (1,-0.5) rectangle (1.2,-1);
	\draw[](1,0) rectangle (1.2,-1);

	\shade[top color = black, bottom color=black!50!white] (0,-0.45) rectangle (1,-0.5);
	\shade[bottom color = black, top color=black!50!white] (0,-0.5) rectangle (1,-0.55);
	\draw[](0,-0.45) rectangle (1,-0.55);

	% Air in mercury tube
	\draw[fill=blue!20,draw=none](6,-0.3) rectangle (7.4,-0.7);
	\draw[fill=blue!20,draw=none](7.4,-0.7) rectangle (7,-1.5);

	% Mercury
	\draw[fill=black!50,draw=none](7,-1.5) rectangle (7.4,-2);
	\draw[fill=black!50,draw=none](7.8,-1.5) rectangle (8.2,-2);

	% Mercury tube
	\draw[draw, thick] (6,-0.3) -- (7.4,-0.3) -- (7.4,-2);
	\draw[draw, thick] (6,-0.7) -- (7,-0.7) -- (7,-2);
	\draw[draw, thick, fill=black!50] (7,-2) arc (180:360:0.6);
	\draw[draw, thick, fill=white] (7.4,-2) arc (180:360:0.2);
	\draw[draw, thick] (7.8,-2) -- (7.8,1.5);
	\draw[draw, thick] (8.2,-2) -- (8.2,1.5);

	\foreach \y in {-2.5,-2.4,...,0.5}{
		\draw[black](8.3,\y)--(8.45,\y);
	}
	\foreach \y in {-2.5,-2,...,0.5}{
		\draw[black](8.3,\y)--(8.55,\y);
	}
	\node[anchor=north] at (7.6,-2.65){Hg-Manometer};

	% Air in valve
	\draw[fill=blue!20,draw=none](4.4,1) rectangle (4.6,0.5);

	% Valve
	\draw[black,thick] (4.4,0.5)--(4.4,1.5);
	\draw[black,thick] (4.6,0.5)--(4.6,1.5);
	\shade[top color = black, bottom color=white] (4.5,1.03) rectangle (4.9,1);
	\shade[top color = white!80, bottom color=black] (4.5,1) rectangle (4.9,0.97);
	\shade[inner color = white, outer color=black] (4.9,1.08) circle (0.08);
	\shade[inner color = white, outer color=black] (4.9,0.92) circle (0.08);
	\shade[inner color = black!50, outer color = black] (4.5,1) circle (0.15);

	\node[anchor=west] at (5,1){Ventil};

	\node[anchor=south,text width=2cm, align=center] at (2,1.2){Umgebung\\$(p_0,T_0)$};

\end{tikzpicture}
\end{document}