WIP Ulthui - How are my rivers?

[Sarithus]

Hello. Here's my WIP map. I wouldn't say I'm that knowledgeable on geography but I've been looking into rivers. How are mine?

- Mostly always into the sea mouth
- They get wider when multiple rivers meet
- They flow faster downhill and go in that direction
- They can also come from mountains

Questions:

1. Beside Alturath I have rivers branching off into nothing. I've done this because I've seen it on other maps, but what causes them to stop?
2. Must a river that goes into the sea always create a delta?
3. Most of my rivers come from the lakes. Does that mean that around the lakes it has to be of lower elevation since all rivers go downwards in the steepest direction, or can they just flow out slowly?
4. Is there anything that happens to rivers that are flowing very fast from steep high elevated regions that I can draw?

Might have more questions later, thanks.