Therapy in your first language, or your second
Why some people find it easier to talk about difficult things in a language they learned later, and why others do not.
People often assume therapy has to happen in a first language. Sometimes that is right: a first language usually carries more emotional weight, and some things can only be reached in it.
But the opposite happens just as often. A later language can put useful distance between a person and something painful, and make it sayable at all for the first time.
Neither is the correct answer. You don't have to decide in advance, as there will be flexibility within each session: sessions can move between English and Persian as they need to.