I suggest you do your own research before following advice from internet forums as you never really know who is advising.
You don't have a DPF problem, you don't have a turbo problem, and you're engine oil is most likely fine.
If you've let it get in to this state we can expect that you've not changed the oil recently or have any mechanical knowledge, unless you have a warning that the DPF is blocked there is no need to touch this.
What is important is that you take this to a competent mechanic, they will reseat the base of the injector seal, it needs to be spotlessly clean and perfectly flat to enable the new copper washer to sit flush and make a good seal, if you're not a mechanic yourself it's worth paying to get this done properly.
If you're interested in how to do it, take a look at page 6 of this guide. This is for the 1.6 PSA engine and not the BMW engine, but the seating of the injector is the same. https://www.hdi-tuning.co.uk/downloa...00HDI-TDCI.pdf
My offer of telephone advice remains