When I pair the smartphone with another Bluetooth source, after a while the headphones turn off. But when paired with just one source, they work perfectly. Maybe I need to do some other operation?

You get what you paid for, build quality is pretty good, headphones don't feel like cheap plastic crap. However sound quality is horrible i guess that's what you get from the cheapest possible over ear headphones. They sound like listening to good headphones through a pillow, absolutely no bass and no tops, sound is opposite of crisp and it is horribly muffled. Cheap buds easily crush these headphones when it comes to sound quality. If you care about sound quality and don't need over ear headphones buy qcy t13 or xiaomi buds you will be good with either of those.

The sound is good and the quality of the material feels very nice 👌

Great headphones, the hearing isn't very strong, but relatively okay for the price.

Great construction, good sound, excellent battery.