Bad Engine Problems Need Help Fast Please Please

Ok just had the engine replaced. First Off this is freaking me out bad. My car has no power. Like it wont climb a hill for shat. And it wont get up and go like it should. Second its overheating like crazy. I mean when im sitting still its fine when Im trying to go or actual moving its starts heating and the fans are on without the whole ac heater trick. Please help I wont drive this car until I get this fixed.

Also had the tranny flushed like reccomended for the mileage and now it shifts like shat and i dont know but it just seems odd.