125er without letter and documents

Hello, I can get a Yamaha DT125R (4BL) from a very good friend who once had a motorcycle workshop, which he still existed a few years ago as his workshop from a customer who bought another machine from him in payment. My friend then put it in the corner, wanted to judge it originally and then sell it, but he never came to it, and meanwhile he does not operate his motorcycle workshop anymore. The Yamaha would be ideal for me to drive it next year when I am 16 with the A1. So, and now to the problem: All documents about the Yamaha are no longer available. Only the keys are still there because they have been stuck all the time, but that’s not a document. Now I have a little bit of a problem with the Yamaha. I can’t find the keys anymore, because they have been put in there, but that’s not a document. On many pages it says that in case of loss of the ZBII you need an oath state insurance of the previous owner, where he assures that he has lost the ZBII, and that the machine is not stolen. Then there is still a check on the KBA, and the whole lasts if’ works 6-8 weeks until you can allow it. But as far as I am informed a 125er has no vehicle letter (ZBII) but only one operating permit?! I look just there e I don’t know what it’s like now, so which papers are needed for a 125-inch, whether this is as regulated as with a large machine, as I can allow the DT … I’ve been researching for a long time, but there’s no real solution. As far as the technology is concerned, I can tell that I know myself, but I didn’t have to deal with the whole registration scram so far. I only have one operating license with my mofa, and I’ve finished it. I only needed a safety certificate, which I then sent to Hercules (today’s SFM) and finished. The new ABE was in the mailbox after 3 days together with an invoice of 29€. But I don’t think that will be so easy with the Yamaha. Would I be glad if you could bring some light into the dark! Greetings