The problem with the entrance (Grand Theft Auto 5)

Hello,the problem is that I forgot the username and password from the gta where I can write to regain access to the game ? and I have another steam ACC with this game ,can I have this ACC to bind to Accu which I forgot the username and password ?
Appealed to those support in the VC sent me was this link https://support.rockstargames.com/ru/articles/200153036/Эта-учетная-запись-уже-связана-с-другим-аккаунтом-Steam-в-Max-Payne-3 ( said the same for GTA V) but even I don't get that there is meant (help please )