How much would it cost to fix my iphone? - 1

I was out with friends yesterday and I went to open my phone and it didn't turn on. A few minutes before it was on 70% battery. But I figured it died because my phone has always been weird with its battery. So I went inside to charge it and it wouldn't turn on. I noticed the lock button felt stuck but if that's the problem why is it not turning on from the charger? I get home and plug my phone into a computer and the phone (after a long period of charging) finally turns on. Everything seemed to be working and when I pressed the lock button it worked even tho it felt stuck. I just woke up this morning and noticed the volume buttons don't work and the silent/ringer switch no matter what will say what you switched it to but the phone is stuck on vibrate. Is there a way to fix everything and how much will it cost?

Please tell us what type of iphone it is, 6 s5 s4?