Geez ..... FIRSt do as the man says and check the gearbox oil levels.
FILL them as specified.
Using the clutch in slipping mode makes the linings very hot ... Like VERY VERY hot ..... like smoke and flames if you try really hard.
After the FIRST time clutch linings get that hot they are jiggered for good, AND the rubbing surfaces of the flywheel and pressure plate may be damaged.
The slightly soft lining gets baked hard like a mixture of cement and glass, all shiny, and the trrouble then it it either grips or it doesn't. It becomes difficult to set off smoothly because the clutch just grabs all of a sudden often with a judder.
Slob will explain the cure ....
CharlesY