Hey there mabdulqadir85,
Thanks for reaching out to Apple Support Communities. I understand the Wi-Fi signal icon is intermittently missing from your iPhone display. You’ve done some great troubleshooting so far and I’ll be happy to help with this.
To verify, does this icon seem to disappear when using certain apps or doing certain task?
If not, based off the steps you’ve taken so far, the next step to take would be to back up your iPhone and reinstall iOS using the steps from these links:
How to back up your iPhone, iPad, and iPod touch
If you can't update or restore your iPhone, iPad, or iPod touch
If the issue continues, restore your iPhone to factory settings and test this out in that condition:
Restore your iPhone, iPad, or iPod to factory settings
If the issue doesn’t continue in factory settings, restore your backup and test once more:
Restore your iPhone, iPad, or iPod touch from a backup
Regards.