Thank you all.
I thought a bit about scale (and a friend of mine helped a bit) and now i know that my rivers are too big or my mountains too small. if the mountains are right the rivers are all like the amazonas, and if the rivers are... yeah normal rivers the mountains are hills and the hills are... molehills. So I will redo this and fix the mountains. I will work on some more mountains too because I think they repeat to much. Or I will use the brushes Schwarzkreuz made, they are really to my taste. But I dont know when I will have time for that :/ much work and some birthdays in family feed my time :/

The basics are very solid, but guessing at the scale, that splitting river probably wouldn't happen.
Would you please explain that (or give a link where I can read about it?= I discussed my rivers and some other geographical points with the mentioned friend and said nothing about that, but maybe he forgot that or he doesnt know that and I always would like to learn something new

The world I'm planing is magical, but I would like to have maps that "could" work in reallity. So I think I have to knwo why the river will prpably not do, what I think he could do.

Edit: I forgot to write:
@Lyandra Its really comforting that im not the only person who has problems with scaling.