Is my iPhone ruined

Use this teardown to start your water damage repair.

Then use the Water Damage Guide for how to clean up the phone. Be very careful. The guide really is important because you don't want further corrosion in your phone.

If you are able to get the phone to turn on, but have no display, you will definitely need to replace your screen. Follow this guide for the screen replacement, then another for the home button, and lastly, one for your front camera assembly. The home button, camera, and LCD shield will need to be transferred since they do not come with the new screen. Definitely be careful with the home button as you will lose touch ID if you ever have to replace it.