What exactly is installed now? Please refer to [HOWTO] Give complete /e/OS version info easily for support, answers, comparison etc on how to find out and paste here.
Via Wi-Fi or mobile network or both?
Does the issue persist in safe mode? … [HOWTO] Reboot into Safe Mode
If the issue is there with internet via Wi-Fi … does the issue persist if you remove the SIM card?
If the issue is there with internet via mobile network … do you have or can you borrow a different SIM card to check?
Do you use an SD card in the phone? If so, in which way did you let the system format it? (Asking because https://forum.fairphone.com/t/a-little-guide-to-using-sd-cards/37297)