IPhone contacts don't display?

It appears my iPhone has deleted about half of my contacts, in my messages app there's a bunch of numbers where there should be names, and they are not in contacts app, also I can't make them new contacts. However if I go to the button to make a new text message and in the "to" bar when I search the name my contact pops up but still displays a their phone number instead of the name. I tried calling apple an they said it would be 20$ for their help so that's not happening.

Go into contacts and of the numbers are there click edit and enter the name. If there's mothing there just go into phone and enter the number it should say add to contacts or edit existing. Chose that one. Of none work then I suggest re bootimf the entire phone and start over. If you contacts are saved with your email then your in luck if not well have fun. And of that diesnt work then well pay the 20 bucks

  • Whatsapp contacts - if they're onnm contacts am I on theirs? I have the phone number of an old friend stored on my iPhone and they also show on my whatsapp contact list… Does this mean that they still have my phone number stored in their phone and also have whatsapp installed on their phone? The chat thing says they haven't been seen since 28th sept? If they didn't have my number on their phone would they still show as one of my contacts on whatsapp?
  • We know that if a smartphone has more than 300 pixels per inch, it is a retina display. How much ppi it need to be a super retina display? It is said that human retina can distinguish pixels and letters in screen seem broken if ppi is below 300. If ppi is above 300, how high the ppi may be, it looks same for human eye, then why iPhone has 458 pixels in iPhone x?
  • People I don't know appearing in iPhone 4s contacts? I have an iPhone 4s, and I just looked in my contacts and found a bunch of contacts that I've never added. It shows their names and numbers, and I don't know any of these people. Does someone else have their contacts connected to mine somehow? I don't use iCloud, by the way.
  • My contacts keep changing into my parent's contacts? I'm using my Dad's old iPhone 4, so it has all of his data. I cleared out everything that was his but I hate the part where each time my parent's add a new contact to their phone, everything syncs over to my contacts, so I'm scrolling down my list and see a new person I don't know but my parents do. Is there a way to change this?