2 problems -reverse falters and trunk hatch won't open-

Hello! I just bought this car and I have found issue that I would like to address right away! (1) In reverse, I have to pump the gas to get her moving and, on a hill, I can forget it. If I just accelerate it won't move and RPMs rise. (2) Also, I sometimes can but more often cannot open my back hatch. The locks work perfectly: I can lock and unlock the entire car by using the key in it, but still the hatch won't open when it has unlocked the entire car.

Sincerely,
Kati Rose

... One other thing! To get a new key made should I contact a Mercedes dealership?