Hey Minyoongayshiz,
I see that you're running into issues with your iPhone 7 not powering on.
Here's a resource to follow for the exact issue that you're experiencing: If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support. If you're still unable to turn on the device after going through the resource, you may want to look into service options.
Take a look here to find some nearby service locations: Apple - Find Locations
Here's some information about seeking service: iPhone Repair - Official Apple Support
You can also start a repair request here: Apple - Support - Bring in for Repair
Cheers!