ok worked for me!
For everybody with the same problems i did this:
* Debian update & upgrade
* disable all plugins
* change domain status with "unknown error" from "torestore" to "tochange"
* started the 1.1.5 auto install
* after successful installation
* enable all plugins
* done
Big thank you to @Nuxwin & @Ninos for your help! I really appreciate it!