For fault codes, which are often only a pointer in the right direction rather than the full diagnostics solution, you could perhaps see if there is someone local to you with a VCDS or suitable machine to see what information it can give. It's also good to have a second independent reading you can see done in front of your eyes and see the readout and have recorded report.
Here is a list of Briskoda members that may be able to help you. - Briskoda VCDS Owners Map (click me)
The car could have something like a turbo actuator fault plus need a regen. The regen does take more than most people realise and a lot more if you are only used to driving the car steadily and over shorter journeys, and you don't want a low tank of fuel.
It may or may not be a crap car, and being an older modern diesel it may or may not be suited to your driving and usage - it could be a good car just with common and easily resolved problems, or not, over the internet no one is going to be able to confirm (at least this early on).
You'd probably not want to do as these guys did and certainly not until you know for sure what the actual problems are and this may not be necessary if other issues are resolved. - https://www.youtube.com/watch?v=j6nIjAglvLw
Personally I'd try to find someone on that list above to at least do a full scan and report and then based on that information consider whether to go for a proper blowout run, or IF I could bounce the car back (despite consumer laws this might not be possible in the real world) or whether to get the repairs and keep the car or sell it on. I've had dealings with the English motor trade for decades so know how things are in real life as opposed to the ideals, theories and laws, if you are dealing with totally dishonest, or totally incompetent or lazy, people it's difficult to get anywhere useful with them. That doesn't necessarily mean you shouldn't try though, you know your situation I don't.