Extender 3110

Hi, all new here so hope someone can help me out....
I have a wireless huawei router but the signal is not strong enough to reach all Arachne the Appartement.
I then Borrowed a netgear wifi extender model 3110 and registered it but called the WiFi names names something else that the Name I use on the router.
Well my questions are:
I see that when passing the extender the WiFi automatically jumps to another channel that I created at the net gear page, all good and works well, but it doesn’t go back to the main router channel when I’m near the router. Isn’t it supposed to do that?!?
Also, my airplay speaker catches up fine as it’s placed near the router, but I use my iPhone to stream from, and it seems when the signal goes from the router to the extender, that the music player can’t recognize it anymore and stops playing😔
Anything I can do to fix this?????

Best regards
Torben