adds signature support:

- save your signature as "signature.png"
- preferably have a transparent background
- adjust the \vspace and \hspace parameters as well as the scale
- enjoy ;)

.gitignore

@@ -14,3 +14,4 @@ document.pdf
 *.fdb_latexmk
 *.fls
 *.synctex.gz
+*.png

document.tex

@@ -15,6 +15,7 @@
 \usepackage{array}
 \usepackage{makecell}
 \usepackage{csvsimple}
+\usepackage{graphicx} % For including images
  
 % Hier die Optionen fuer scrlttr2 eintragen. 
 % S.a. scrguide.pdf ab Seite 150
@@ -83,6 +84,11 @@ Es wird bestätigt, dass die Zuwendung nur zur Förderung der Bildung, von Wisse
 
 \footnotesize
 \closing{Mit freundlichen Grüßen}
+% Adjust vertical space as needed with \vspace
+\vspace{-70pt} % Adjust the space above the signature as needed
+% Adjust horizontal space as needed with \hspace
+\hspace{-20pt} % Adjust the space to the left of the signature as needed
+\includegraphics[scale=.9]{signature.png} % Include your signature image
 
 \tiny
 Hinweis:
@@ -111,6 +117,11 @@ nach § 60a Abs. 1 AO länger als 3 Jahre seit Ausstellung des Bescheides zurüc
 \begin{flushright} Summe: \summe{} \euro{} \end{flushright}
 
 \closing{Mit freundlichen Grüßen}
+% Adjust vertical space as needed with \vspace
+\vspace{-70pt} % Adjust the space above the signature as needed
+% Adjust horizontal space as needed with \hspace
+\hspace{-20pt} % Adjust the space to the left of the signature as needed
+\includegraphics[scale=.9]{signature.png} % Include your signature image
 
 \end{letter}
 \end{document}