Hi Plamen, welcome back to OSM! It's great you are making edits in a part of Sofia where we don't have many mappers.
However when editing objects that have changed, please consider to add a lifecycle prefix instead of deleting them. These football fields, for instance, are still visible on aerial images, so if you completey deleted them, someone else may see them on images and add them again, not knowing that they can't be used any more. It's then better to add disused: or abandoned: to them. If they get repaired, it's also easier to just remove the prefix than to draw them again. Same for shops that are empty, buildings that have been demolished, etc. See https://wiki.openstreetmap.org/wiki/Lifecycle_prefix
Pozdravi, Richard