Iphone 7 temperature getting to 40 celsus while gaming is it normal

If the game uses a lot of processor power and it is internet connected and you have a weak internet then yes it can.

But just in case go to Settings > Battery > Health and see what the percentage is. If it is 80% or lower, or you get a warning message there, get the battery replaced.

So you just recently put a new battery in your iPhone?

Mrapple ~ Was the new battery put in by a qualified technician using a genuine iPhone battery?...

About genuine iPhone batteries

Repair Provider Verification - Official Apple Support

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