DSL performance is bad

Hello,

Firstly apologies for writing in English, my German is very bad.

I have had o2 DSL for 6 years at my apartment with little problem. 4 years ago I upgraded to VDSL - since then I have always been able to get a download speed of 35-40mbit/s without issue. I've also had my router (o2 Box 6431) set up as modem only, connecting via PPPoE Pass Through from my Apple Airport Extreme.

On Monday my internet connection went down - I received a letter from o2 telling me they were upgrading something, giving me a new username and password as well.

Firstly, I am unable to use this username/password in my Apple Airport - It is reporting no PPPoE server connection, so I had to factory reset my o2 Box and use this for my internet connection. With some firmware update at some point the option to use PPPoE Pass Through is now no longer present, is it possible still to use PPPoE Pass Through?



Secondly, my performance is degraded - now my connection is running at 20mb/s maximum. As I primarily use my internet connection to stream Netflix 4K this is not good and makes 4K content unwatchable, with buffering and pauses.

Can anyone help me? Or recommend a way to either talk to someone in English in customer support or provide a written way to report faults? (The email address I used to report a fault in 2013 no longer functions)