I'm currently working on a .xml to .uml diagram converter, but you may also add relations/attributes/operations and change pretty much everything. but drawing multiple arrows between 2 classes would cause one to override the other one pretty much, i guess that's not the intention
Is that allowed by UML? Because i can not really find an example on the internet.
Yes, of course you can have several association between two classes.
You can find a practical example here, where an account has borrowed or reserved books.
For the more theoretical aspect, you need to understand that for a class C, every attribute A has a type T, and that this attribute could be replaced in the diagram with an association of C with class T (the name of the attribute being shown on the T side of the link):
