Extremely High TA and Ph

Hello, since last year I have only been using liquid chlorine. Unfortunately, I did not track my Ph and TA and decided to check it for the summer and it is extremely high. TA was 400 and PH is 8.2. I tried about a gallon and half of Muriatic Acid I had from last year and after measuring a week later I am at 390 and 8.2. Any help will be appreciated. I am planning on getting more muriatic acid tomorrow. Thanks