[Tex/LaTex] Caption above with the use of adjustbox and footnotesize under picture

Question

I am trying to rotate a figure with the adjustbox statement as mentioned in Rotate picture with caption. How ever I cant force the caption to be above and not below the plot inside this Code. Also I am trying to place the text of the footnotesize below the figure (at the place of the actual caption). Here is a short reproducible example

\documentclass[a4paper,12pt]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage{amsthm}
\usepackage{mathtools}

\usepackage{adjustbox}
\usepackage{float}

\begin{document}
\section{Appendix}
\begin{figure}[H]
\begin{adjustbox}{addcode={\begin{minipage}{\width}}{\caption{Graphische Lösung: Veränderung der Konturlinien
     }\end{minipage}},rotate=90}
        \includegraphics[width=\paperwidth]{example-image-c}
        \label{fig:Lasscases}
        \end{adjustbox}
    \footnotesize{RSS und $t$ sind die Werte, bei denen die kleinste Konturlinie die Ecke der Raute tangiert *Das Beispiel unterstellt:  $\beta=(0.36, -0.1)$.}
\end{figure}
\end{document}

Answer 1

You mean like this?

\documentclass[a4paper,12pt]{scrartcl}
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage{adjustbox}
\usepackage{float}
\usepackage{caption}

\begin{document}
\section{Appendix}
\begin{figure}[H]
\begin{adjustbox}{
  addcode={\begin{minipage}{\width}
           \caption{Graphische Lösung: Veränderung der Konturlinien}}
          {\captionsetup{font=footnotesize}
           \caption*{RSS und $t$ sind die Werte, bei denen die kleinste
                     Konturlinie die Ecke der Raute tangiert *Das Beispiel
                     unterstellt: $\beta=(0.36, -0.1)$.}
           \end{minipage}},
  rotate=90}
\includegraphics[width=.88\paperwidth]{example-image-c}
\label{fig:Lasscases}
\end{adjustbox}
\end{figure}
\end{document}