hey dudes!There is one thing that drives me nuts!!!

1.) I fly boeing 737..and I have no problems with heading to the runway but please somebody tell me why the hell I can't get my boeing down on the runway?..namely..my nose goes up and won't let me decrease the altitude.I didn't even touch that altimeter hold switch or anything ..I kept it manually all the time..so what could be wrong?

another question:
Please tell me how to activate an autopilot aproaching? I tried by clicking on the approach buton but nothing happened.

I'd really appreciate your help mates...thanks in advance