1996 Other BMW models Car Lock

Other Category problem
1996 Other BMW models Engine Size unknown Front Wheel Drive Automatic 75000 miles

Hello - my car door doesn't shut properly unless you really swing the door quite hard - and then it closes fine.
I am worried that by having to slam the door we may damage it further - could you tell me what you think the problem is and is this expensve to fix, in your opinion?
Many thanks - D