Learning JOSM is not so hard as it looked like at first. Now that I know JOSM a bit I never want go back to Potlatch. With Potlatch I produced so many mistakes! Now with JOSM I found the problems and could iron them out. Accuracy is so much better. This is what I looked for. Only the OSM tiles in the background layer have way to low resolution and are not really helpful. Maybe I can change this somehow?