I thought you cannot login if you don't have the code from authenticator, like steam guard. He has really good rep on other forums and he was curious about moving to epicnpc, asking to lend him my account. I was a bit hesistant but I considered the option, since he seemed trusted, that is why i recently changed the password. My bad then, I thought he won't be able to login at all. I don't think it would be fair to ban him as "scammer", as he provides a quality service of steam hours boosting. He didn't mention having an account here, so I will need to inquire further about this.
Just to sum it up, I changed the password to the same as on the account he is boosting hours for me. It would take me some time to find the phone i activated the authenticator app on anyway and also the time to think it over without fully declining him, or at least so I thought. I am sorry for the inconvenience. Is there any chance to remove the multi account on my profile?
PS I will change the pw to my old one then