Galant EA0 coupling problem

Hello together, have a problem. For some time now I have to go to my Galant when he stood for a while and especially in cold weather, the clutch pedal completely push through to switch the gears. In addition, the gears then go quite hard and the clutch pedal goes very slowly or almost not back to his starting position. The Galant has about 130,000 km. If I then drive for a while and the car is warm, the situation normalizes, I can also switch normally again and the clutch pedal can be operated normally. What could this be about? Maybe ventilate the clutch and change hydraulic fluid? Thank you for your help! MfG Killuminati