Hello Fabian,
I am happy to help with this:
1) The current latest version of WP is 5.5.3 (not 5.5).
2) When going to WP page “Add Plugins” to find “Advance Forms”, it shows a warning “Untested with your version of WordPress”. I guess this indicates that you have not confirmed yet its compatibility with 5.5.3 Am I correct?
3) I installed and activated the plugin. Then I checked page https://advancedforms.github.io/guides/basic/creating-a-form/ to see how to create my first form. There is a picture depicting the dashboard, and showing that I need to select the tab “Forms”. However, WP dashboard does not show “Forms” anywhere. So there is no way to create a form.
Based on both points 2 and 3 above, I came to realize that the plugin is not working. Accordingly, I reviewed it to warn others.
Of course, once you solve points 2 and 3 above, I will be happy to update my review