Hi ramiz03,
Thank you for using the Apple Support Communities. We understand that since updating the software on your iPhone 12 mini the iPhone has been experiencing lagging issues. Have you made sure that the iPhone has been updated the latest iOS 14.5? Updating to the latest version of iOS provides the latest features, security updates, and bug fixes. Make sure to back up your iPhone first. You may also want to check to make sure that your iPhone has enough storage too.
If you still have issues check out the resources below for more helpful information:
If your iPhone, iPad, or iPod touch won't turn on or is frozen
Update your iPhone, iPad, or iPod touch
How to check the storage on your iPhone, iPad, and iPod touch
Let us know if this helps!
Take care.