You’ll really struggle if it’s dead, dead. I’d take it to a phone shop and ask if they have a new battery they can temporarily fit to try and power it on to get your data off it. If it doesn’t boot your next step is a micro soldering specialist to see if they can find and repair the issue why it’s dead. If that doesn’t work then you’ve lost your data I’m afraid.
I take it it’s not backed up to Google?