My water ph is very high it 7.6 how to reduce it ??

you can use sodium biphosphate sold by LFS as PH down.
You can also use peat and have some in a filter.
Reverse Osmosis will also remove the mminerals from the water and should drop the PH closer to 7.0.

What fish do you want to keep because 7.6 isn't really that high and unless you are keeping wild caught fishes, most should be fine in that water.

Hardness stabilizes pH. Generally water with a higher pH is harder. You can try to add chemicals to lower the pH, but due to the hardness it will rebound back to its original value.

Unless as stated you are keeping wilds, or breeding a particular species your pH should be fine.

Actually what is the peat ?? sorry for my ignorance

http://www.aquacave.com/detail.aspx?ID=994

You can also use garden peat moss in a media bag, as long as you are sure no fertilizers have been added. Cheaper is usually better in this case.

peat is a soft brown fibrous substance. It comes from peat bogs and is really old decomposed plant matter. It can be bought from nurseries and garden centres. Some has fertiliser added but most don't.