Hi @ines3, sorry to hear about this. 
Do I understand correctly that when you are starting up the device, it gets stuck at the Sony logo? If that is the case, try removing your SIM and SD card(s) and start the device up with neither of them mounted and see if that helps.
If you still aren't able to fully boot it up, try performing a software repair using Xperia Companion, but note that this process will delete all data stored on the internal storage of the device and without being able to boot up the device, the program can't create a backup.
Let me know how it went!
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