I dropped my iphone 6s and only the top right corner cracked, but the screen has vertical white lines;?

The lines are not opaque and change color according to the colors displayed on the screen (i.e. Yellow produces red lines, etc.) Also the very right side of the screen is unresponsive and the rest of the screen keeps opening random apps and pressing random things. Calls still come through and the audio is fine. My question is, what's broken/needs fixing and about how much would it cost?

Is it insured? Most likely not as you are asking the question - however some bank accounts offer this insurance as part of a bank account when you opened it, and many people don't even know this. Similarly your house contents insurance or car insurance it might cover your mobile without you knowing. If you are still living at home with parents their bank account might cover this or their house insurance.

Apple will charge the most for the repair. A small local Apple repair specialist in your area might be cheaper. Browse for one in your area - but ask for a quote first and tell them that the cost must be fixed as you are on a tight budget.

In the end it might be cheaper to upgrade to a new contract - especially if your current contact is near its end and then you upgrade to iPhone 7 (or any iPhone 6s would be cheaper upgrade for a new contract) you might pay a little more monthly for the model 7 but at least you have the latest working phone. Failing that many people have upgraded to iPhone 7s and therefore eBay and secondhand shops and Craigslist have loads of deals on used iPhone 6s options that might be cheaper than a repair.

Take it to a couple of cell phone repair shops to get an estimate, also take it to an Apple store for the same. The Apple store will pretty much be spot on for the repair (they will more than likely replace the entire screen.