Hello and welcome to the Pelican Forum (AKA: The nut house).
First of all you will need to give a better description of which 944 you have - what year, and is it an NA, Turbo, S or S2, or Base.
A great source for all kinds of working knowledge for our 944's is:
Clark's Garage Home Page you may use Clark's allot, I know I do.
On the problems with the shifter go to Clark's Garage then on the left side of the main page choose Garage Shop Manual - Then go to "T" for transaxle - then shift mechanism repair. Once there you will see a diagram of what the shift mechanism os all about.
Your problem may be #10 which is a nylon cup bushing that the bottom of the shift lever sits in. the bottom of the shift lever has a ball on it and it sits in the cup bearing, that may be worn out.
If you are referring to a loose screw that could be the problem with the short shifter (Mounted above the Transaxle in the rear of the car). On the diagram at Clark's look at the #19 Set Screw. That set screw is supposed to be safety wired to keep it from loosening. That set screw fastens the rear running shift rod the the Short shifter with a coupling collar. If that is the problem be careful that it doesn't come completely loose as then the car will not shift at all - the rest of that section at Clark's Garage should be very helpful.
Clark's Garage will be very helpful for all of your 944 mechanical endeavors...
Have pfun -
__________________
78-924 traded for 80-931 traded for 84-944 traded for 85.5-944 (7th one now).

UAV-M1 (Urban Assault Vehicle - Model 1)
Bless the lowered, and pass the nitromethane.
Pedal to the metal till you see the gates of hell then brake
NLA - No longer available is a four letter word