I went to a fish store to get my water tested and everything was off the charts what should i do

3 of my fish died

If the readings were off the charts, it means you have excess ammonia and nitrites in your water, by products of the nitrogen cycle is what is killing your fish, highly doubt it is your ph itself, though a higher ph will make ammonia in your water more toxic. Chemical treatment of your water is not the answer really. You need to establish and build up a biological filter is what you need. If you have another established tank or where you bought your fish from will let you have some of thier gravel you can speed things up that way. Bottled products like cycle, and foil bagged Bio Spira produce inconsistant results to advocate using that. What size tank do you have? You have both fishless and using fish options here to complete your nitrogen cycle. Since you have a population in there, might as well just finish out with it at this point.

1. Cut the feedings down to reduce waste and excess food in the water, those are the biggest contributers to ammonia in your water.

2. Perform a 30-40% change in your water now to begin lowering the ammonia and nitrites in the water to under lethal levels.

3. Get a testing kit to monitor the progress from here on in. If you can get gravel or filter media from an established tank, use that to speed things up.

The only thing again on your ph you need to focus on is if it's 7.8 and up, it's going to play into ammonia toxicity, and of course above 8.0 going to really cause ammonia to be that much more toxic. Don't adjust the ph, rather work on ammonia control as mentioned above.