My greatest problem is that the phone was sold as brand new. The first bad sign was a missing screw at the bottom. I could have live with that, but the phone proved to be unusable. It bricked every time a SIM card was inserted. After a long but unproductive conversation with the store and with their agreement I've sent the phone to a local service. According to the service's report, the phone was massively "serviced" previously. Changed cables, water damage indicator turned to red, etc. Look at the pictures, even the serial numbers don't match. I can imagine that a recycled phone somehow got back in the system (the phone - except the missing screw - looked like new, well packed foiled in original box) The store offered me the possibility to return the phone, they even offered a 20-30 dollars service budget. Sending back to Chine is not an option because of the shipping costs. Because the mainboard must be replaced, the service costs exceed the offered amount.
Although I encountered certain issues, the seller was quick to address them and was very reasonable and patient toward me. Excellent service and trustworthy seller.