ACCOUNT WAS CHANGED CREDENTIAL WHILE PLAYING

so i was just playing at night and suddenly a pop up says my steam credentials was changed i checked my email and it has no notification of changed password or anything but before this happend i accidentally pressed a appece.exe something like that and it temporary broke my browser(chrome) and after a day somebody took and hackd my instagram but it was nothing but then my steam also was changed its credential i tried to recover the password but the email that was connected was no longer linked idk what happend my acc was very very important to me i hope i can get some help i also did a bunch of virus scan but nothing was found

please help me my acc is very important to me