Need Help ASAP for a 1993 Jetta lll
 

I have a 1993 VW Jetta that has some issues and cant find anyone to help me resolve them. First off when i drive it doesnt always switch gear and will slip and rev up. Alot of the times i come to a complate stop and the car stays at 15 grand and wants to accelerate. Normally its supposed to be a little under 10 grand. If i put it in park at that point it will rev up to 30 grand and stay there. Lately i been losing power and it wants to die. The last problem is, is that i did a full tune up and my gas mileage is not so good and my needle bounces around alot. So there are many problems or just one im not sure. Im new to VWs. Hope someone can help me out here. Thank you.