Help with phone situation?

I'm still making monthly payments on my iphone 6s, but a family member sold me an iphone 7 for really cheap. Its brand new and just has a cracked screen. I would just switch over phones but will i have to keep paying on my iphone 6s until its fully payed for?

Should I get an iphone 7 or stay with 6?

I love my iphone 6 but It just broke after 2 years so I was thinking about getting the 7. I'm going to either get another 6, 6s, 6+, or 7, which one would you recommend?

Water damaged iPhone 6? Is it gone forever?

I was stupid and dropped my iphone in water. I've never done anything like this before and I didn't know what to do so I dried it off and put it in rice. I tried to turn it on while it was in rice to see if the screen was damaged and it wasn't so I turned it off again. I tried to turn it on again to see if the water damage wasn't affecting anything else. The touch screen was working and most of my apps were except for snapchat. However this time it turned off itself and tried to reboot but got stuck on the apple logo. Right now its sitting in rice and thats all I can do rn since is late. Do you think its really badly damaged. I'm shaking as this is my first iPhone and i'm scared i will never be able to fix it or that it will be too expensive. I bought the phone off someone else so i can't go to apple can I? It seemed completely fine until it turned back off. I'm so scared.

How to solve the photo issue on iPhone 6s?

I do quite a bit of selling on Ebay so take lots of photos on my phone. Since I got my phone earlier in the year, I've been struggling to sort this out.

When I take a photo, it works fine as I can see it in my phones album as a picture.

When I connect my phone to my pc and browse in the folders to copy the pics to my pc to use, they show up as movies or movie clips.

No mater what setting I've used on my phone camera, they appear in the folder (on my pc) as movies.

P.S: this is my first ever iPhone

Why does my small amount of photos take up so much space?

On my iPhone 7, I have only 76 pictures/videos. When I click manage storage, it says that they take up 1.3 gb of space, while my friends have hundreds of photos but when they click manage storage, it only takes up a couple hundred mb. Why do the photos take up so much space on my phone or how can I fix this problem?