Two week old fairphone 4 e/os crashed down and don't restart

[Volker]

You don’t need a PC/cable.

Following the link, ignore what’s written below and click on the topic above:

And to make it easier for you here is the link to the topic:

Hard Reset / Factory Data Reset

Hard Reset / Factory Data Reset What is this? This kind of reset erases all data from you phone and sets it back to factory settings (the way it came when you bought it). This can sometimes be necessary if your phone is soft dic:bricked or otherwise majorly screwed up. How do I do this? Before you do this you should definitely create a thorough dic:backup if possible. If you can still boot your phone you can perform a reset in Settings → System → Reset Options. If not, you’ll have to go thr…

To sum it up:
press vol-up while starting your phone (and keep it pressed until you reach the recovery system) and select “factory reset” in the recovery menu.