Diagrama de flujo/estructura de Tesis con tikzpicture

Question

Para mi tesis intento (re)construir un diagrama de flujo para su estructura. Pero estoy luchando... Puedes ver el borrador en la imagen.

¿Alguien puede ayudarme? ¿Existe alguna herramienta o algo útil?

Intenté adaptarmeeste, pero no funciona correctamente.

edit: vale, ahora gracias a tu ayuda logré acercarme a lo que quiero. Pero es demasiado grande... ¿cómo puedo solucionar esto?

\documentclass[a4paper,12pt]{scrbook}
\usepackage{enumitem, tikz}
\usetikzlibrary{calc,positioning,shapes.geometric,fit}
\begin{document}

\begin{figure}[H]
\begin{center}

\begin{tikzpicture}[block/.style={regular polygon,regular polygon sides=4,
    inner xsep=1em,align=center,text width=7em,draw},font=\small,thick,
    box/.style={draw,align=center,inner sep=1em},>=stealth
  ]
 \begin{scope}[local bounding box=blocks]
  \node[block] (B1) {TextTextTextTextText TextText Text Text
  \begin{enumerate}[label={\alph*)}]
   \item Kapitel 1
   \item Kapitel 2 TextTextText Text Text Text Text Text
   \item Kapitel 3 Text TextText Text
   \item Kapitel 4 TextTextText Text
   \item Kapitel 5
  \end{enumerate}};
  \path let \p1=($(B1.east)-(B1.west)$) in 
  node[right=3em of B1,block] (B2) {TextTextTextTextText TextText Text Text Text Text};
 \end{scope} 
 \path let \p1=($(blocks.east)-(blocks.west)$) in
  [nodes={minimum width=\x1},node distance=2em]
  node[box,above=of blocks] (A) {\textbf{Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text}}
  node[box,below=of blocks] (C) {Text Text Text Text Text Text Text Text}
  node[box,below=of C] (D) {Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text}
  node[box,below=1em of D.south west,minimum width=12em,inner ysep=1ex] (E) {Experteninterviews}
  let \p2=($(D.south)-(E.south)$) in
  node[box,below={\y2+1em} of D] (F) {Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text Text};
 \path[->] foreach \X in {1,2} 
    {(B\X.north) edge[<-] (B\X.north|-A.south)
     (B\X.south) edge (B\X.south|-C.north)}
    (C) edge (D) ([xshift=4em]D.south) edge ([xshift=4em]D.south|-F.north)
    (E.east) edge[edge label=Text Text Text] ([xshift=3.9em]D.south|-E.east);
 \node[draw=gray,thin,fit=(A)(C),dashed,rounded corners=0.8em,inner sep=0.8em,
    label=right:\rotatebox{90}{Theoretischer Teil}]{};
 \node[draw=gray,thin,fit=(D)(E)(F),dashed,rounded corners=0.8em,inner sep=0.8em,
    label=right:\rotatebox{90}{Empirischer Teil}]{};
\end{tikzpicture}

\caption{\label{fig:flowchart} Thesis FLOWCHART.}
\end{center}
\end{figure}
\end{document}

Answer 1

¡Bienvenido! Esto es para darle un comienzo.

\documentclass[tikz,border=3mm]{standalone}
\usepackage{enumitem}
\usetikzlibrary{calc,positioning,shapes.geometric,fit}
\begin{document}
\begin{tikzpicture}[block/.style={regular polygon,regular polygon sides=4,
    inner xsep=2em,align=left,text width=5em,draw},font=\sffamily,thick,
    box/.style={draw,align=left,inner sep=2em},>=stealth
  ]
 \begin{scope}[local bounding box=blocks]
  \node[block] (B1) {Concept 1
  \begin{enumerate}[label={\alph*)}]
   \item bla
   \item blub
  \end{enumerate}};
  \path let \p1=($(B1.east)-(B1.west)$) in 
  node[right=3em of B1,block] (B2) {Concept 2};
 \end{scope} 
 \path let \p1=($(blocks.east)-(blocks.west)$) in
  [nodes={minimum width=\x1},node distance=2em]
  node[box,above=of blocks] (A) {Thesis}
  node[box,below=of blocks] (C) {Combination}
  node[box,below=of C] (D) {further analysis}
  node[box,below=1em of D.south west,minimum width=12em,inner ysep=1ex] (E) {Experts}
  let \p2=($(D.south)-(E.south)$) in
  node[box,below={\y2+1em} of D] (F) {Conclusion};
 \path[->] foreach \X in {1,2} 
    {(B\X.north) edge[<-] (B\X.north|-A.south)
     (B\X.south) edge (B\X.south|-C.north)}
    (C) edge (D) ([xshift=4em]D.south) edge ([xshift=4em]D.south|-F.north)
    (E.east) edge[edge label=Bla] ([xshift=3.9em]D.south|-E.east);
 \node[draw=gray,thin,fit=(A)(C),dashed,rounded corners=0.8em,inner sep=0.8em,
    label=right:Theory]{};
 \node[draw=gray,thin,fit=(D)(E)(F),dashed,rounded corners=0.8em,inner sep=0.8em,
    label=right:Empty]{};
\end{tikzpicture}
\end{document}