Hey Markus,
I noticed you checked ‘Yes‘ to reverting back to the default WP theme and deactivating all other plugins as outlined in our Testing for conflicts guide, but can you please confirm this? If possible, send over your System Information as a private reply.
Regarding issue #1, can you test a few different browsers on mobile (Chrome and Safari) and let me know if the results are the same? Please make sure your site is in “Testing for conflicts” mode before troubleshooting.
Thank you for reaching out and have a great rest of your Friday. Cheers!