OK I changed my clutch and is all back together and my slave will not hold oil I fill it up then I have pedel but after about 1/2 hour loose pedel is soft and no oil now can't see where it is gone but wanted to know is it possible to leak inside

Exactly what "oil" did you put in there? Look under dash and see if you see wetness at the clutch pedal push rod.

If the clutch master cylinder reservoir is full of brake fluid, the problem is air in the system--it doesn't take much.