I have everything that you can do.
1. Remove all the muck
2. If the water is still brown yet it has no mud left, super chlorinate the pool using 6 bottles of chlorine and a bottle of acid from your local pool store and pour all of them in at the same time. Wait and run the filter for 24 hours.
3. Wait 2 days and take the water for testing.
4. You're done.
Optional 2. You're done.