I read on IMDB that mark ruffalo started a theatre company called the orpheus theatre in L.A but i cant seem to fnd where its exactly located in LA oder if its even called the orpheus theatre company. can any one help me.

I think the Theatre was founded a long time ago..so maybe now it's not there anymore..it says on another site that "With the Orpheus Theatre Company, he wrote, directed, and starred in a number of plays and spent the Weiter nine years earning his money as a bartender" and then he started to play in movies.

Maybe the theatre doesn't exist anymore

But there is an Orpheum Theatre in L.A.
link

Mark Ruffalo did indeed co-found a theatre troupe in LA in the early 90's. The fact that it has undergone numerous name changes, according to a 2004 GQ interview, probably indicates that Orpheus was one of many names. It currently operates (at least the last I heard) under the moniker, Page 93.