clutches,Car won’t go into gear. 2002 Audi A4 Quattro

My car suddenly wasn't able to let me shift in to gear when I was driving . When the car is off I can easily put it in to any gear. The only only way I can get it to move is to put the car in gear (1st) when it's off and start it, after struggling a bit it will take off. But ones I get out of the gear I am unable to put it in any other gear.

My clutch pedal kind of feels ligher.
It's almost like the car is in gear and pressing the clutch doesn't disengage the gear that it's currently in.

My car has 140000 miles.
My car has a manual transmission.