Thanks for the quick reply.

One can easily think that the software knows what it's doing, but reality is strange and we need to check first ;)

There is an easy way to completely undo those changes, yes:
https://wiki.openstreetmap.org/wiki/Change_rollback

I usually use
https://revert.monicz.dev

You can add the two CS numbers and let the tool do the work. Leave a nice explanation in the comment and you're done.

The other way of fixing this: Check your work using osmcha.org and only undo things that are clearly not right, like the things I mentioned above

in case of questions there's always c.osm.org or one of the signal groups:
https://wiki.openstreetmap.org/wiki/List_of_OSM_centric_Signal_accounts

cheers