TWRP for Fairphone 3

I can’t get to twrp on my phone. Maybe a stupid question, but do you get into twrp in the same way as in the PF2?

‘2. Start TWRP by keeping volume up and power pressed for 10s or so during power on. If you boot it for the first time, it asks to enable write permission for the system partition, which is not needed for updating TWRP.’

And if so, does this mean that twrp is not permantly installed on my phone?

tnx!