I am not able to make wifi calling

Settings, Phone, Wi-fi Calling

If the option is not there talk to your network provider to activate it.

You also seem to be on battery power save mode? Turn that off in Settings, Battery

Weak wifi signal.

Did you reset the router like I advised?

Did you forget then reconnect to wifi like I advised?

Settings, Wifi

Forget the network on the (i).

If it is your router perform a Hard reset to factory settings. Usually requires a paper clip. Google it or check the user manual.

Connect the phone back to Wifi