Long story short, I got an iPhone 7 plus which lost its sound, gets stuck on logo while booting for a long time.
Important note, that the speakers do not work only when calling.
Contacted Apple, basically they said that they are aware of this problem, but do not fix it (my insurance ran out 2 weeks ago). Had the nerve to offer me a purchase of a new phone. They mentioned that this is probably an audio chip problem.