I noticed one of the other people said to only do preacher curls for biceps, I would also do a hammer curl as it hits your brachialis. I’d also recommend following more of a push, pull, legs split twice a week. You’re currently hitting legs in one way or another three times a week which can prevent you from recovering properly. If you want help structuring push, pull, legs just let me know
Hammer curl hits both. PPL and upper/lower are both great and I’ve done both for extended periods and had great progress. I was recommending PPL due to their current split somewhat resembling PPL. I feel as though UL is for more advanced lifters that can push themselves to true failure and minimize the number of sets needed per muscle group to be time effective