it’s ok when executing a command render

It is not normal that you have done some (but not all) of "Running renderd for the first time" at https://switch2osm.org/serving-tiles/manually-building-a-tile-server-20-04-lts/ , have then gone on to do "Running renderd in the background" below, and then gone back to do "Running renderd for the first time" again.

If you're following a recipe to make a cake you can't go back to previous parts or do things in random order - you'll end up baking the icing or have a cake with raw eggs in it.