Is it forbidden to give or get a loan? Does it refer to jews vs non-jews relations? What about Heter Iska, is it related to jews and non-jews? thank you

Shalom! There is actually a positive mitzvah to lend money to Jews without taking interest. It is forbidden to give or take a loan from a Jew with interest, unless you have a Heter Iska contract, or at least mention in writing that it is based upon the Heter Iska. Regarding non-Jews, one can give or take a loan with interest, as is accepted everywhere in the world, and there's no need for a Heter Iska with them.