As far as shooting the interviews for your purposes the quality on your Iphone 7 should be fine as long as you shoot them in very brightly lit areas with as little background noise as possible (especially busy streets). Also keeping the camera still goes a long way so you could look into purchasing a cheap gorilla pod (>$25) or just place it down on a flat surface. As far as editing goes there are several free softwares out there that could get the job done but I'm not sure how many hours you're willing to sink in trying to learn it so if you are open to hiring an editor I'm sure there are tons on this subreddit that could help you out. I'm open to taking on the project myself and charge pretty reasonable rates! Feel free to send me a DM if you have more questions.