The water pump came off!!
Sorry, but every small step is a little victory to me. For me this is the first time that I do something major on a car. Although for others it might be a simple job.
This evening I first tried James' tip to cut the gasket with a knife. Unfortenately, this did not work for me. After that I tried to tap it carefully with a (steel) mallet in all directions, like Waqas wrote. This worked. Slowly it came loose.
Now I could investigate the pump. There is indeed little play in shaft, about 1 mm. Tomorrow I will order a new one.
I also have removed the little U-shaped air vent pipe. James, do really think it's wise to replace the little hose beneath the thermostat? Then I have to remove the thermostat also. But at this stage it is rather easy, off course.
James, about your 5th point: I have a pulley which is suitable for 3 belts. The belt runs over the third slot, closest to the engine. The assembly is as follows: water pump - extra hub - pulley (for 3 belts) - clutch/fan. Because the total length of the short pump plus the extra hub is equal to a long version pump, I think I could swap this assembly for a long version pump. But I am not sure. Tomorrow I will call my dealer. Perhaps he can clarify this.
Does anyone know the exact type of the five bolts for the waterpump? What kind of material is this?
James and Waqas, thank you both for your support. It is nice to know I am not alone in this.
Martijn
P.S.: Waqas, I am surprised you are informed about European soccer! So far, Holland is doing really well. We have won all three matches and now we have qualified for the quarter finals coming saturday.