Can not charge my OnePlus3t

I am useing my One Plus 3t since 2 and a half years now. I love it, but now I have a Problem where I can not charge my phone anymore, because a warning pops up: Temperature is to low, even tho its in my hands at 30°c. I downloaded an app where I can see the status of the Accu. When i can not charge it, the app says the temperature is at -40°C. At one point it randomly switched to 26°C again and it charged again, but often i hhave to wait hors/days with 0%. Pls help :(