I am probably doing something wrong but if I save a edit in Mapedit and then change something else and save again it automatically overwrites the old save.

This happen when I updated new added POI's and saved. Then saw that a newly burned down building (that has been converted to tarmac) was still there in maps I removed it (I hope) and pressed Save again.

I didn't get a chance to update the change-log. It just added the removed building to the change-set. So now the change-log is wrong (see #9005130).

So if anyone is wondering why there is a, hopefully, removed building in the change-set but it is not mentioned in the change-log I truly apologize. I just started with OSM and can only you read this before chastising me. :)