Expert Transmission Issue

It definitely could be low gearbox oil. That can cause the pressure sensor to trigger. Have you checked the oil level? If it's low, that's your first step. A faulty pressure sensor could also cause similar problems, but checking the oil level is a cheap first step. The 'emergency mode' you describe is a common symptom when the transmission isn't getting enough lubrication or pressure.

Where exactly do I check the gearbox oil level on this model?

It's usually on the side of the gearbox, often a dipstick or a fill plug you remove and stick your finger in to check. However, given the symptoms and error code, and considering you don't know where the fill point is, I'd suggest getting it checked professionally. Driving it in 'emergency mode' could cause further damage.

Thanks for the advice. Took it to a workshop, you were right: low gearbox oil. They topped it up and reset the sensor. Cost 365€.