Short version:
My mate helped me out, and it works perfectly now.
Long version:
Had problems getting the bolt holding the clutch in place off. I thought, I had figured it all out, using a chain wrench to hold the bell in place put into an iron tube, giving it support from the floor, so it wouldn't slip. I then used an ordinary wrench on the bolt and had a go at it with a hammer in order to loosen it. It didn't work. I couldn't keep the clutch bell from slipping in the chain wrench.
I pulled quite a few hairs out of my scalp at that point.
I texted my friend about my problems, and he replied, I should use an air powered impact wrench. Luckily there is such one in the workshop where I live, but I have never used such one before and didn't know how all the tubes are supposed to fit together in order for it to function. I got an introduction from my neighbor and got started. It seemed to go well. Only it didn't. At. All.
I managed to turn the bolt into something much rounder than a bolt is supposed to be. At this point I said some very bad words in a somewhat loud voice. And pulled out some more hair.
Called up my friend, and he was kind enough to pass by and fix everything up with his magic touch. In a matter of minutes, the clutch and the clutch spring was replaced with new spare parts and the Kymco Agility 50 was once again working like a charm.
So - there I was, a bit closer to having a bald head, thinking that this just might be the beginning of a great career for me in the business of mechanics.