I made a backup on my old phone, and did test it: restore works fine. But when I copy it to my new phone a problem occured:   restore fails. On both phones I didn't use a login pincode or such sorts.  Can anybody help me? The error message is:

Attention!

Sorry, the backup file seems corrupted!!

Solved. The problem seems to be that I did copy the file to my Window10 computer and from there tot my new phone. But when I used the cloud connection on both phones to copy the file, restore did work well.

Thanks for updating @croc :)