Hi @Ryan31, sorry to hear about this.
Your question has been translated to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
Do I understand correctly that when you reach around 50% battery left, the device just turns off due to low battery? If that is the case, are you able to power on the device again or do you need to plug it in to a charger and charge it for a while before you are able to power it on again?
If it just turns off even though the battery level in the device is high, try performing a software repair using Xperia Companion, but remember to backup your data before you perform the repair as it will delete all data stored on the internal storage.
Should there be no change, there isn't that much that can be done as the Xperia C3 has reached it's end of support and spare parts are no longer available at authorized service centres.
Let me know if that helps!
