Wrong account, sorry.

railway=abandoned (or Abandoned Railway preset) means "The track is gone, but there are still traces" E.g. Gravel, ties, embarkments, tree lines etc.
It does not mean "The track is out of service and overgrown." That would be railway=disused.

Yes, i did. However, i didn't know about shop=butcher, so i didn't search for it. But did it now and removed 95 duplicated features.
On the second example; I wouldn't be able to find it anyway, since it's not tagged with man_made=works, industrial=slaughterhause, or anything at all except name.

Industrial=slaughterhouse: They were listed with the "North American Industry Classification Code" "Poultry Slaughtering, Dressing, and Packing". However, there was a more detailed "processing only"-tag in the orginal data - and i didn't realize it either. But i fixed this too, 700 slaughterhouses remain.

foot=yes is the default value assumed on highway=path's and does not need to be added.

If i would try to fix everything i see, i'll be sitting here until my last day - without break

Please be a bit more careful. way/184762906/history is certainly not a power generator.

Good that you are fixing problems, however, you don't have to pay attention to these "outdated tag" warnings on powerlines. It adds only useless tags that pollute the database and add no value. It adds the wikidata item for Georgia Power and especially useless, the wikipedia page for GAPower. The normal operator tag is enough, the additional tags are basically duplications.
(Note that i mapped almost all of these lines)

Leftovers - fixed. Thanks for letting me know!

These buildings would be better tagged "demolished:building=yes" for now - otherwise, people like me will come along and see "missing" buildings on the aerial images and re-add them.

Thanks for the edit, looks good!

Thanks for your edits! However, a few small things to keep in mind:
- When drawing buildings, you can square them by pressing the "Q" key (when the building is selected).
- Adresses: The state adress should be "SC" instead of "sc", the road name should be "Narrowleaf Avenue" instead of "NARROWLEAF AVE". Besides that, the edit looks good.

Please use demolished:building=* next time.

If you don't understand railway=abandoned, don't delete it. Reverted.

Thanks for letting me know. I fixed them, the last one was already broken - i will delete it later.

Note that many of the deleted relations here were already broken.

what a horrible problem whole map is broken now!1!1!!!!

Hello, thanks for your edits/additions! They are very helpful. However, to make them even better, you could tag old, obviously demolished features such as way/422944949 as demolished, e.g. change the "building=yes" to "demolished:building=yes". This prevents overlappings with your new roads and old, nonexisting buildings. (the example creates currently 6 error messages due to overlaps)

Looks good! Thanks for your edits.

This was a remain from a very old import. Your edit looks good, welcome to OSM!

Of course i reverted it - on the other CS, i said if the tracks are deleted again without good reasons, i'll restore them.

He has nothing to decide here - only if it would be obvious vandalism or copyright violations. He can provide his input on the matter. However, since this input are just lies/obvious untruths, I certainly won't listen to it.

"OSM is to map what is currently on the ground" - yes, the traces are on the ground.
"If you need to check historic maps to map something and cannot do it based on a field survey" - really now? I have to mention the maps, because you seem to think that the remaining tracks and all other obvious traces there were placed for fun or something.