Bridging a WiFi connection and access point

Situation

I have an unlimited 4G internet plan with my phone which I use to create a WiFi network for my PC, smartphone and OSMC. However the phone does not broadcast the tethered WiFi network all the time, meaning I have to enable it manually every time a device wants to (re)connect to the network/internet. This is somewhat annoying.

Since my RPi 3 with OSMC is running all the time I figured I’d make it broadcast a secondary network which would be used by all devices and bridge it to the 4G WiFi network.

I plugged a WiFi dongle in the RPi 3, so the primary RPi 3 antenna (wlan0 I guess) is connecting to the smartphone. Then I enabled WiFi to Ethernet tethering, to my surprise this “secondary” antenna (wlan1 probably) created a network and did not stop the wlan0 connection (great job guys!).

Question

How to tether these two WiFi networks with OSMC? Instead of wlan1 to eth0 I’d like to do wlan0 to wlan1. Is this possible? How would one do something like that?