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

Try reset network settings. Also try removing SIM card and put back in. If neither works call your network provider n see if its on their side

I suspect you simply need to update your APN (Access Point Name) settings. These settings tell your phone where to find the internet server for your wireless carrier. The settings may have been lost in the upgrade.

There's good news and bad news here. Bad news: Apple (being Apple) doesn't allow you to enter these settings on your own. Good news: There's a website that will do it for you… Free and fast:

Open the site on your phone (you'll need Wi-Fi): unlockit.co.nz… The website will ask for your wireless carrier. It will then create a profile and install it on your iPhone (or iPad).

No, you can't go back without a computer. Does the phone not connect with either data or Wi-Fi?