How to draw shape as 'curved arrows' with text (with tikz)

Question

I would like to draw the figure below with Tikz. My research on the web to draw a curved arrow with text yielded nothing.

On the other hand, I wonder how to direct the arrow to the left with the text not upside down.

\documentclass[tikz]{standalone}
\usetikzlibrary{arrows}
\usetikzlibrary{calc}
\usetikzlibrary{shapes}
\begin{document}
    \begin{tikzpicture}[semithick,x=20mm, y=20mm]

        \node[single arrow, draw,single arrow tip angle=100, align=center] [rotate=0] at (0,0) {Test \\ test test};
        \node[single arrow, draw,single arrow tip angle=100, align=center] [rotate=180] at (1,0) {Test \\ test test};

    \end{tikzpicture}  
\end{document}

Who can help me 1. Draw shape "curved arrows" 2. orient these arrows correctly

Answer 1

I wouldn't actually actually use the arrow nodes for this, but draw very thick lines with arrowheads and add nodes afterwards. However, you need PGF 3.0.0 for fine control over the arrowhead parameters:

\documentclass[border=0.125cm]{standalone}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
\begin{document}

\tikzset{%
  thick arrow/.style={
     -{Triangle[angle=120:1pt 1]},
     line width=1.5cm, 
     draw=gray
  },
  arrow label/.style={
    text=white,
    font=\sf,
    align=center
  },
  set mark/.style={
    insert path={
      node [midway, arrow label, node contents=#1]
    }
  }
}
\begin{tikzpicture}

\draw [thick arrow]
  (-6,0) -- (-3,0) [set mark={Processues \\ de d\'emarrage}];

\draw [thick arrow]
   (-2,0) -- (-2,1.5)
   arc (180:0:2 and 1.5) [set mark={Processus \\ de planification}]
   -- (2,0.5);

\draw [thick arrow]
   (2,0) -- (2,-1.5) 
   arc (360:180:2 and 1.5) [set mark={Processus \\ d'ex\'ecution}]
   -- (-2,-0.5);

\draw [thick arrow]
  (3,0) -- (6,0) [set mark={Processues \\ de cl\^oture}];
\end{tikzpicture}
\end{document}