Thanks to your help I was able to create some basic things with TikZ. However I run into trouble when creating a larger image without all straight lines. I dont know how to get the line between the box EIB and Parter Re through BNP. I'm also struggling a bit with getting the text nice but that is not my main issue. It would be great if someone could give some advice! It will be appreciated
\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{arrows, positioning, quotes}
\begin{document}
\begin{tikzpicture}[
node distance=10mm and 29mm,
box/.style = {draw, minimum height=35mm, minimum width=20mm, align=center},
sy+/.style = {yshift= 2mm},
sy-/.style = {yshift=-2mm},
every edge quotes/.style = {align=center}
]
\node (n1) [box] {\textbf{Investor}};
\node (n2) [box,right=of n1] {\textbf{EIB}};
\node (n3) [box,right=of n2] {\textbf{BNP}};
\node (n4) [box,below=of n3,minimum height=20mm] {\textbf{Partner Re}};
%
\draw[very thick,->, transform canvas={yshift=2em}]
([sy+] n1.east) to [above,"Issue price \\ \hspace{2cm} \\ \hspace{2cm}"] ([sy+] n2.west);
\draw[very thick, dashed,->,transform canvas={yshift=-2em}]
([sy-] n2.west) to [below," \hspace{2cm} \\ \hspace{2cm} \\ Notional $\times$ realized mortality rate"] ([sy-] n1.east);
\draw[very thick,->, transform canvas={yshift=2em}]
([sy+] n2.east) to [above,"\footnotesize Interest rate swap \\ \hspace{2cm} \\ \hspace{2cm}"] ([sy+] n3.west);
\draw[very thick, dashed,->,transform canvas={yshift=2em}]
([sy-] n3.west) -- ([sy-] n2.east);
\end{tikzpicture}
\end{document}