auto tranny535i

About 7 months aggo my car stoped moving when i was driven for about an hour i immediatly thought oh no this has to be the tranny.
I went to the tranny shop and let them do what they had to.
After i got my car al together again i noticed a strange soun was comming from the tranny and there was a lot of drag like the clutch didn't move freely.
I went back to the shop they told me it couldn't be the tranny but most likely it's the torque converter.
they told me to go find a seccond hand an that's what i did.
But now when i'm driving and my tranny starts warming up its like when i'm in first gear the clutch engage en immediatly diss engae when the tranny has cooled down i't drives normal.
But yesterday i went for a drive and when i put the gearshift in r the engine stalled. when istarted it up again ireved to about 2000 rpm and put it in reverse it went normal and there was nothing strange about the tranny no strange noises are what so ever please reply.