help needed!! 1series 120D 55plate

Two things, firstly i struggle to get my car into reverse, 1st and 2nd gear but once ive put it in another gear like 4th 5th or 6th it works fine in the lower gears but only for so long then the problem comes back. Secondly my seatbelt alarm keeps warning for the passenger seat when the seat is empty unless i drive with the belt buckled all the time. ive checked the sensors under the seat and they look ok, cant think of anything else(this only started after i had a velet done the other day).

thanks guys.

Sounds like a clutch issue hard to get into low gears but when driving goes in easier and check the plugs under the seat havn't been damaged or unplugged sounds like occupancy sensor on the seat have it scanned to show any airbag codes might just need reset from wiring being disturbed