Questions about Philips TAT2206WT/00

Hello, I have an issue, that most of the time only one ear is working. I already activate "mono audio" in the bluetooth settings of the phone but when I place both in the ears, only one is working. Anyone had the issue or knows if this is a setting somewhere to be changed? I dont think one ear is miss-functioning as each time it is a different ear which decided to play the music. Thank you!

With my headphones, one of them can no longer be charged. What should I do in this case? Is it more the case with the charging case or the headphones?

These headphones seem to be only partially compatible with Garmin watches. They do connect, but the music is permanently playing at full volume.

I need a charging cable for these headphones. Can I buy them separately?

Can these headphones also be used on Iphone X? If so, do I still need an Apple charging cable?