dropped iphone 7 only showing apple logo for a short time then turns off

The phone is very likely going to need to be taken to an Apple Store or authorized Apple Service shop for repairs or replacement.

It's a shot in the dark, but you could try a Forced Restart to see if that might help, since that is the first thing that the Apple Store or repair shop will do when you take the phone to them.

Force restart iPhone - Apple SupportOfficial Apple Support › guide › iphone › ios

swaxxyyy ~ Does your iPhone 7 still have its original battery?

And, if it comes back to life, what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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