Fairphone just flickers grey then turns off

I dropped my phone today, and it was fine for a while but now it does not turn on. I press the power button and for a fraction of a second it shows a grey screen but then turns off. If I hold power and vol up it goes to the boot menu, but if I select any option it just turns off again.

Also I am in Uganda - shipping to Europe is not really an option for me at the moment! Hopefully I can fix it myself with some adviceā€¦

try to write at the customer service