I have a ford ka 2013 the clutch pedal as because very lite  I can't change gear, the pedal doesn't stay down checked the oil level and all OK 

3 hours ago, Leemead said:

the clutch pedal as because very lite  I can't change gear, the pedal doesn't stay down checked the oil level and all OK

 Take it to a garage

As your car is made by fiat and not Ford you have the advantage that the clutch slave cylinder is on the outside of the clutch bellhousing and not inside it.  So you can see if it moves when you depress clutch pedal. If it does move then the fault is probably inside the bell housing , if it doesn’t then it is probably the hydraulics. Is the pedal connected properly to clutch master cylinder?  Is there correct fluid level supplying master cylinder?  Follow pipe from master cylinder to slave cylinder.  Is the pipe secure at both ends, any sign of fluid leak, check whole length in case chaffing has rubbed through the pipe.