I can't fault Back Market's support, it's very professional, Arlin was great and his colleagues followed up well.
As for the JBL Tune 520BT headphones themselves, they're very pleasant to wear, very practical, the bass is incredible, there's even an app with default sound settings that aren't bad. However, the headphones aren't finished! The highs and mids are almost non-existent compared to the bass, so you have great bass but an incomplete sound, I do not even know how it is possible to miss it as a creator of sound accessories like JBL! So for 100€ it's too expensive and given that I needed full sound because I bought these headphones for my music studio, even with the 50% off sale, it wasn't worth keeping them.
JBL need to bring out the same headphones again and correct this gross sound defect, and then we'll have incredible headphones that might even be worth at least €150!
I hope this message helps you and goes back to JBL.
Best regards,
Axel.