Problem shifting gears

[#1_M.I._CARLOS]

I hate making post for these kinds of things, however after about an hour of researching I haven't been able to find something to help me.

Here is the problem
When I start the car in neutral and I try to switch gears I doesn't let me, I can only go into 3rd gear but the gears grind very loudly.
HOWEVER, if I switch to first gear while the car is off and then turn the car on it does start but the rpm's are very low and it feels like the car wants to turn off on me.
The clutch lost all the pressure but The fluid levels are normal, what could cause this?

[Mike1357]

The only thing that comes to mind is either a bad clutch matter cylinder or bad clutch slave cylinder. Not having pressure won't allow the clutch to disengage and let you select a gear. It also may be that your clutch is slipping real bad if you can start it in gear with no clutch pressure and not move. An easy easy to tell if your slave cylinder is bad is to pull back the rubber boot. If fluid comes out, it's bad.

[Tishock]

Quick tip:

Raise the car, so that both front wheels are off the ground. Now start the car in neutral. The wheels will spin on their own, but very very slowly. If they're spinning quickly, then the issue is your clutch and not the hydraulics.