Since I couldn't find the solution online, I'll just show you the problem:
[img]file:///C:/Users/Rainer%20Irrsinn/Pictures/Screenshots/Screenshot%20(1).png[/img]

I don't know if you can even see the picture...the problem is that the brush is just thick. But it should start with a thin end, like displayed in krita.
I have no idea why it changed. It's one thick line when I try to draw.

Please help.

A couple of problems with your post:
First you posted this in the wrong sub-forum. You probably wanted the Krita General Help sub-forum.
Second the image will need to be hosted somewhere online such as imageshack (you can browse the posts over in that sub-forum to see what other users use as well).