Sudden Problems: Phone cannot restart, phone signal low or non-existent, several settings missing [Xiaomi.eu, Miui 10]

Hi everybody, since around two days I am having more and more problems with my phone, which I until now did not have any issues with whatsoever.

Firstly it stated by the phone just turing off again some time after starting. Now this problem disappeard but others appeard.

I noticed the fingerprint sensor to unlock the screen did not function anymore. So I went to the settings to re-apply it. There I noticed there is no option for this fingerprint unlock anymore all of a sudden. Also, I...

Sudden Problems: Phone cannot restart, phone signal low or non-existent, several settings missing [Xiaomi.eu, Miui 10]