Sorry for the dumb question... but how do i go over the opening tree/database of another chess.com player while at the same time have an engine running to provide the evaluation. I managed the first part but in order to get the engine in it seems i have to leave the database / opening tree?? I know from lichess that the engine can alwyas be turned on and off on any view of the board but i cant find the button here.
The Explorer option doesn't have an embedded engine. That feature is allowed in Daily games and engines are not, so it's unlikely to be added.
However, you should be able to use Learn > Analysis and the Explorer tab there should be usable.

Sorry for the dumb question... but how do i go over the opening tree/database of another chess.com player while at the same time have an engine running to provide the evaluation. I managed the first part but in order to get the engine in it seems i have to leave the database / opening tree?? I know from lichess that the engine can alwyas be turned on and off on any view of the board but i cant find the button here.