If you cant prove a hypothesis, then how do scientist learn?

Hypotheses must be provable. If scientists cannot prove a "hypothesis" right or wrong, they need to change it to a legitimate hypothesis - something you can prove.

If it is proven wrong, they can change certain aspects of it to make a more specific experiment.

Scientist learn by doing the experiment over and over again. When they complete it, they learn what to do and what not to do.