Permission denied on function after schema copy
After hours of reading of documentation I found that PosgreSQL first searches pg_catalog schema even before all schemas listed in search_path.

So checked pg_catalog catalog and I don't know why but my function was defined there and user postgres was the owner of the function.

I just deleted my function from pg_catalog and it's OK and works perfect as expected.

I still don't know how the function got there in pg_catalog.