Suggest to repair at workshop, repair procedure as below:
1. Dismantle the transmission assembly, take apart the clutch disk.
2. Inspect the worn level of the clutch disk, replace it if the rivet is exposed.
3. Inspect the worn level of the clutch pressure plate, replace it if the surface has obvious uneven mark.
4. Check the clutch release bearing and replace if necessary.
5. Check the clutch pump (clutch cable) and replace if necessary