Betta Fish: Update on my betta Ruby that I’m trying to save

First, thank you to everyone who has tried to help me with my fish. I have been doing 20 to 25% water changes morning and evening and the master test kit this morning showed the following:
High Ph: 8.0
Ammonia: 0
Nitrite: 0
Nitrate: 0
He still doesn’t seem interested in food, but I do think there’s been some improvement. The water is a little brown due to the Mopani wood. I added last night. Temp is 77 a little low. I think the water was a little cold when I changed it today.
Should I continue to do the 20% water changes twice daily? And continue to test every morning? And for how long? Thank you in advance I am happy he’s still alive! Please send prayers and good vibes!