first of all its a gsr trans its hard for me to shift into gears every now and then
sometimes i have to keep playing with it for the gears to go in sometimes i have to shift into second cause first gears wont go in and it takes forever for me to shift into reverse... what could it be???? im not now trans guru lol

 

My first guess would be something with your clutch, try bleeding out the clutch system first.

 

did you check the trans. fluid?
id swap it out and run full synthetic.

 

I use to have that issue a while back...turned out that my front passenger transaxial had a seal that needed to be replaced so it was leaking oil...
once i put a quart of oil in it..boom...alll fixed

you might wanna check to see if that's the same case with you