I Want Downgrade Ios 14 to Ios 13. How I Can do that..?

The first day or so with a new release will consume more power as data gets rebuilt.

Also look for malfunctioning apps; for apps consuming excessive power.

Downgrades are available for and are authorized for only for a very limited window after a new release, and require an existing backup of the older environment, and a computer running current software, can cause data loss, and the downgrade a comparatively complex undertaking. Details:

https://osxdaily.com/2020/09/19/how-downgrade-ios-14/

“Downgrading is a technical process that could theoretically lead to issues, and without compatible backups you may experience permanent data loss.“

Sorry but you can’t go back.

Sell your device if you are not happy.