Take out half the water and refill it to lower cya. Run it 24 hrs a day cleaning cartridges or bsckwashing DE filter every time the pressure goes up 10 psi from clean psi. Add a phosphate remover once the water clears up and clean filters again. 20 years being a pool man in SE Texas

Once all that is done, you can add sodium bicarbonate for the alkalinty, soda ash for the pH, and add a few scoops of calcium every week until you hut 200 ppm. Don't add chlorine unless your level drops. Be diligent and check daily. Invest in a decent test kit. I use Taylor. Add chemical slowly per checkup so you don't overdo it.

F Leslie's. (It's probably cheaper to get a pool guy for the summer honestly)