Hi,
Your Golf has a DPF that doesn't require additives, and you also have VCDS. I would recommend forcing a DPF regeneration using Grips, so that it reaches a higher exhaust temperature (which you can see in VCDS – exhaust temperature before the turbo exceeding 800°C at 2000+ rpm with little load). Then, just before the end of the regeneration cycle (monitor the "ash content" value), drive the car into the workshop on a lift.
Then have the DPF removed and assessed/cleaned based on
https://community.dieselschrauber.org/en/viewtopic.php?t=24243.
If the DPF is damaged or cannot be cleaned for any reason, I would replace it with a refurbished DPF.
The free pipe length can be determined using a wire. For assessing the exhaust back pressure, there is a corresponding measurement topic.
https://community.dieselschrauber.org/en/viewtopic.php?t=24222
You can then use the money you've saved to go on a nice vacation or invest it in back massages.
I have already removed my DPF several times for research purposes, with mileage ranging from 220,000 km to 70,000 km, and a brand new DPF, if freshly regenerated, shows no significant difference. As long as the ash can be removed and nothing is broken or damaged, I would have no reservations about cleaning the DPF or using a cleaned replacement part.
Best regards, Rainer.