Trouble with switching from Polylang to WPML

Hi,

I would switch from Polylang to WPML, but I run in trouble with the page.
If I deactivate Polylang to let run WPML, all existing pages will be blank, but all content is still there in the editor / Dashboard. I try a lot of things to fix this problem, but nothing works. Default language is German and there are only some test translations in english, who are not important.

What I try:
1: I check the box to delete Polylang completely in the Polylang Settings
2: I try to let import the Polylang stuff with the “Migrate Polylang to WPML” Plugin
3: I search for some hints in the Database (but not sure for what I need to look exactly…
4: I try to change the language Settings of Polylang to english or set up the same settings for the German language of WPML to Polylang, before I start the migration.

Any Help or ideas?

The page I need help with: [log in to see the link]