XPS 13 9360: no bootable devices

Hi

I have a xps 13 9360 with windows 10 and bios 1.3.5. today my laptop went low on battery so i plugged it in and pressed continue on the low batterie warning. It straight went to some diagonaitics that didnt have any result. After a restart it shows the dell logo for a few seconds and then goes to the dell support assist screen which says: no bootable devices found. How can i fix this?

Thanks and best regards

Stephan