Trunck Latch and Door Locks

I am completely new to this forum, but I've had my 1995 Golf III for 9 years now. Lately, I have experienced a locking problem with my doors and trunk. My rear driver side door will not latch when you attempt to close it, instead it bounces back. I can fix the problem by keeping a small screwdriver with me and carefully poking at the latch (it works, still don't know why). I've greased the lock on the door itself and the point of impact on the body of the car. Normally, I don't open that door b/c its a pain to close.
Next, I am having serious trouble with my trunck lock. Even more frustrating is the water thats leaking into the trunk. The lock will not unlock. I see rust building up around the locking mechanism. Has this problem occured to anyone? Just wondering.