How to prevent the submersible pump against corrosion and if it is affected , how we can repair it ?

What's wrong with it? Most sub pumps are Stainless Steel. Mine is 12 yrs old and has never failed to work and hold pressure.

I agree, mine is about 15 years old at my home in Georgia. If a person can not work on them theirself, and the cost is so low, normally if they stop working, it is not worth taking them to a shop for repair.

Of course I am considering a smaller home unit.

What type do you have, how large and what is wrong with it