RPM drop when releasing the clutch?

I know the clutch will lower RPMs usually, but this is a little different. When starting to move, in first, letting off the clutch should normally be smooth. My problem is that it will instantly drop 500ish RPMs and sound like its going to stall. I plan to check brake fluid for the clutch, the slave cylinder and the rest of the clutch that i can see before taking the car apart. I will record a video of what im talking about, and maybe im just bad at driving manual, but it did not used to do this.

what im doing:
1) Giving gas as letting off clutch. RPMs stay around 1000.
2) when clutch gets to biting point, it instantly drops 500RPMs. Even when im giving it gas.

Thanks for any input i am given! What all shpuld i check when i have the car on stands?

RPM drop when releasing the clutch?