Reving hi when aplay the clutch

When on ignition Battery warning light missing...but when check using omh meter charging system K...how to find this fault code

My car displayed engine light and i took it for diagnosing,they found that problem is oxygen sensor. I bought another oxygen sensor but problem still exist

Press my horn on steering wheel and I hear the relay clicking, I can find the actual horn so I can change it

When you drive its fine its When you change gears it revs up. Can't find the problem any suggestions please. Have to free in gear for few seconds and then change it drops revs other wise if change str…