clutch stuck and cannot shift gears?

Hi, I pump the clutch pedal a few times and bled the slave cylinder outlet. Gear then shifted well. vehicle stood a couple days and the same problem came back. Bled again and the problem temporally went away again. Found that transmission fuel had a lot of suspension black particles. Cleaned the reservoir and bled the line again and the problem went away temporarily. So, I take the slave out and drained the line until clean fuel came out. Replaced with a new slave and pumped the clutch. Could not bring back fluid pressure. Then replaced the clutch master cylinder but also could not bring back fluid pressure. Please suggest what was wrong.