@jayarajtriparna this "power button is not working for switch off and volume button also not working" sounds like a bad flex cable. The power button and volume buttons are on the same flex. Replacement flex cables are readily available at many online stores.
To replace the power button flex. Since iFixit does not yet have a guide for that , use something like the one For that use something like the one [https://www.nadiemellamagallina.com/en/manuales/smartphones-1/realme-1166/realme-7-pro-1251/pulsador-de-encendido-11163|from here] It was written in Spanish so use a browser that can translate it for you.
While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
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