Hello!

High chlorine levels can give you a high/unaccurate ph reading.
After shock it could take about 8 hours, even more for the chlorine level to come down.

Once your chlorine is at a stable reading (2-3.0)
You can test the ph and alkalinity again.

If your ph and alkalinity are still high you can add muriatic acid to lower both numbers.

Post back and let us know what happens! Thanks.