@vtxyzzy, Thank you so much for your answer! I had a feeling I did something like that, and solution should be related to working with wp-config.php file, but couldn’t google the right answer as couldn’t formulate my problem in correct terms. THANK YOU VERY MUCH for not passing by and giving a hand.
Now I’m only waiting for the owner to send me the correct login info for the backend, so I can access those php files..
Good luck with all your technical endeavors!
