Clutch fluid problem

Hi everyone,

I have a problem with my cutch pedal which don't come back.

I tried to purge air bubbles from clutch fluid. It fix the problem for 10 minutes...
So seems I have a breach in the hydrolic clutch circuit (no problem on brakes) but I don't saw anything.
Nothing behind the pedal and nothing near to the fluid tank.

Also if you have documentation or tuff like that which can help me, I wiil be happy with that (mostly on gearbox removal, if I need to replace the clutch receiver).

I tried to find the master clutch cylinder but I didn't find it. So if you have idea of where it is 😁
(left side driving)

Thanks in advance for your help.
PS: I'm a French guy so, sorry if my English is not very good 🙏