When will my symptoms go away is the million dollar question. I would expect significant improvements within 3 weeks. If not your dosage is too low. And 1,600 Mesalazine is a crazy low dose. You should be 4,800 mgs a day plus an enema (another 4,000mgs). These medications are anti-inflammatory, the higher the dose, the quicker the recovery.
I'd call your gastroenterologist-specialist and ask for a higher dose of Mesalazine (4,800mgs) and a 4,000 mg enema. Give your uc a solid one-two knockout punch, get your quality of life back, and move on