Q: reseting wifi connection

Hi there, monika.l!

Thanks for reaching out to the  Apple Support Communities! It sounds like you are having issues with your  Wi-Fi staying connected. I know how important it is to be able to maintain  Wi-Fi connection at all times. First, go to Settings on the iPhone, then General, and then to Reset. Once there, tap Reset all Settings. This will reset the iPhone settings, but not erase personal information such as photos, contacts, or music. It will, however, remove Wi-Fi and VPN settings so be sure you have those settings and passwords ready for when the iPhone is started back up.

If that doesn't work, it would be a good idea to be sure there is not a software issue as the root cause of this for you.

1. Check out this article for the steps for How to backup your iPhone, iPad, and iPod touch. 
2. Use this article for the steps to Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings.
3. Once that is done, set the phone up as new and test the phone to see if the issue is still going on. Then, follow this article to Restore your iPhone, iPad, or iPod touch from a backup

Cheers!