Trouble shifting

ok heres to 4-1, im having a serious issue with my 03' Jetta Wolfsburg, its a manual and i think it has to do with the clutch. i've beat the shit out of this car since it was my first one as a daily driver. well i am having trouble shifting into reverse and third, i know its not an issue with pushing the clutch pedal in all the way cuz i've made sure i've pushed the pedal in all the way and it still happens. it seems every once in a while after i shift into a gear it pops out, but its only for reverse and third. i can still drive but im not stupid enough to do it, since when it pops out its still locked in gear but it sits there and vibrates.

any help or suggestions would be much appreciated

Clutch

Check out the shifter cables & hope it's not an internal trans problem.

i checked what i could from under the shift boot from inside the car, everything was the same as it always has been, but my clutch pedal seems loose. so im thinkin its the clutch