Fixing iPhone 6S WiFi issue

My iPhone very often has unstable connections. It’s connected to the WiFi but has no internet access. I’ve tried resetting the network, rebooting, and forgetting the network but it doesn’t work. Then I found there seems to be an easier option: just enter wifi settings and hit the blue i icon and then you’ll see the following interface. Simply hit the renew lease button on the bottom and voilà! You’re online again!