IPHONE 6 PLUS doesn't connect INTERNET?

I updated my Iphone 6 plus to iOS 11. But now I have a big problem. It doesn't open Facebook and Instagram. Nor does it connect to App Store. Safari doesn't work either. It seems like I have a problem with the phone's network settings. I tried different networks but the problem prevails. How can I fix this? Can I go back to using iOS 10 without using a computer as I don't have it with me right now?

Added (1). I can connect to Wi-Fi and use cellular data. Still, can't use Internet.

Added (2). Whatsapp works well but Facebook, Instagram, Safari, Chrome and AppStore don't work

Added (3). I see:
SSL Problem
No Connection
Untrusted Server

Can an iPhone SE withstand 150 degree heat for 15 minutes?

When I use the sauna at the gym I put my iPhone into a locker. But I would rather keep it with me. Would it survive 150 degrees for 15 minuets? Would a small insulated lunch bag help?

Added (1). For those who ask: Can't you live without your phone for 15 minuets?
The gym has a sign that says leave valuables in your locker or your car.'
However, they also say the lockers in the lobby are safer than lockers in the changing rooms.

Which iPhone Should I Buy? - 1

Okay so my parents are letting me get an iPhone this year. And I will only have about $500 to spend. I'm wondering is the iPhone 7 plus good enough? Or the iPhone 7? You see my service I'm run on is Metro PCS. And so I need to find out what's good and what's not.

I had never had an iPhone before. This is my 1st iPhone in 20 years. So maybe you all can teach me a little bit about iPhones.

My iphone speaker doesn't play when I press on it?

I have an Iphone SE, approximately one and a half years old. However, for some reason, the speaker will not play sound properly. If i take it out of my apple phone case, it plays, but if i press on the speaker, the sound either mutes or muffles. Any help will be greatly appreciated.

How to unlock iPhone? - 1

I got an iphone from ebay and it's locked, I can't contact the owner. Is there a way I can somehow unlock the iphone or take it to the store to to unlock it?