Issue 1 happened during an update from version 220.127.116.11 to the latest stable one.
After the DB restore, the shop itself run well, but the admin backend run into an error
solution: download and install the 18.104.22.168 version and copy the src directory from the fresh one, renamed first and deleter afterwards the corrupt one.
Upgrade of modules was not possible: classes/../tools/pear/PEAR.php): failed
solution: removed blockrss module and replaced other corrupted modules which run into the same issues from modules of fresh installation