How to reverse renal function from mild or moderate stage to normal stage? Egfr is 60.

Depends. It depends on the root cause of the renal impairment as some are not reversible. In general, it is a good idea to stay well hydrated, however.
Maybe. Some causes can not be reversed, but make sure you are not taking meds that adversely affect kidney function, both prescription meds (including some meds for high blood pressure) and otc meds, including nsaids like ibuprofen.
Might be hard. Key is to prevent further loss. Gfr goes down with time. Treatment of high bp, diabetes, not smoking, doing exercise can help. Avoid nsaids and drink adequate fluid. Ironically, acei/arb are BP meds that worsen GFR but can protect kidney function long-term. 60 is still pretty good, and better hydration before test may make number look better. But most important to modify factors that damage kidney.