BMW Repair: 84 533i loss of clutch pressure, brake fluid reservoir, clutch master

Question
I have recently purchased an 84 533i and at first the clutch seemed fine then after two days of driving i lost pressure. I'll explain as best i can, when i first drove it the clutch had resistance from 75% to the floor when pressing down. Then in one days time it dropped to 50% to the floor, and then it dropped again down to maybe 15-20% to the floor. Now i have nearly lost all clutch pressure, i checked the brake fluid, it was low but over half so i filled it. I did not see any clutch reservoir, so i am assuming that the clutch is fed from the brake reservoir. I have no more ideas as of what to do any advice would be great.

Answer
The brake fluid reservoir is also the clutch reservoir. If it is low and the pads are ok I would suspect either the clutch master or slave cylinders.The master cylinder would leak inside,you would see moisture on the carpet under the pedals.The slave cylinder is harder to see but can be seen by jacking the car up and looking at the cylinder itself to see if it wet.I would look at both to see which is bad.