Why is my screen partially unresponsive and has vertical lines on it?

Again, I'm no expert and you should wait for a more reputable user to respond but since no one has responded yet I'll throw in my two cents. If there are lines on your screen it's most likely your LCD that's damaged. You can take it to the apple store and if you're lucky they'll replace it for free, but if not they might charge you about ~$120 for a screen replacement. If you're confident in your repairing skills it can actually be quite simple, and be much cheaper to fix yourself. Front screen replacements can run you anywhere from ~$30 onward depending on the distributor and quality. If you're gonna go on the route of doing it yourself you could always try unplugging and replugging in the LCD cable connectors, one cable could possibly be loose. But mind you doing the repair on your own could cause more damage if you're completely clueless of what your doing. If you're still unsure but feeling bold, and want to save some money as well as earning some experience, check out this guide:

iPhone 6のスクリーンの交換

as well as some YouTube videos. Good luck my friend. Again, be extra careful, use plastic when removing cables to prevent shortages, and make sure the right sized screws go in the right spot cause that can cause a problem on its own.