Why do my emails gone missing in my gmail account?

So I check a email on gmail account on my iphone using the MAIL app, I have received and read a few emails. Later the day, I logined in gmail using my laptop, I couldn't find those emails I read earlier. They are not even in " All Mail. What's happening here? Is it just some settings that can be fixed or I was hacked?

Ck your gmail settings. There's a setting to "remove from server"

  • Why does gmail sign me out of my account every time I close my safari app on my iphone? This is a recent development and I'm starting to get really irritated. It started happening today after I cleared my history. Before today, I could close all my apps and when I opened them I would still be logged into my gmail account. This is no longer the case, and I'm not sure why. I cleared my cache and enabled cookies, so I don't understand why gmail is doing this. I've probably tried logging into my gmail account 10 times trying to fix this.
  • Why does gmail keep moving emails to trash? Recently gmail has started moving emails from certain senders to the trash (not spam) automatically. Senders include Groupon and LivingSocial but also a wildlife newsletter, amazon and some other newsletters. I only access my gmail from Chrome (maybe once a month) and the Mailbox app (by Dropbox) on my iPhone. I have no filters or additional folders set up. How do I make it stop?
  • Why are other peoples emails remember when I go to sign into gmail? When I go to sign into gmail on my laptop (which I let NO one use) there are other peoples emails remembered. They are: strong.jordan678@gmail.com atottionna@gmail.com hmonggirl94@gmail.com I've never seen those emails before nor do I know anyone with them or let anyone sign in on my iphone (chrome remember on all devices). Why would that be happening?
  • How to unlink my Outlook account and my Gmail account? A while back, I linked these accounts together somehow (it's been so long I forgot how) so I would only have to access one account to read all my email, but now when I get an email in my Gmail account, I get that exact same email in my Outlook account a few minutes later, and I keep getting notification noises on my iPhone and have to spend time deleting the extra emails. It's really annoying me and I want to undo it, but I don't know how!