What percentage of German gas was arriving from Russia in Nordstream when it was blown?
Zero, since it was shut down "for scheduled maintenance" at the time. The Russians were driving a hard bargain. Somebody wanted that negotiation to stop.
[Spoiler: of course, I believe that "somebody" was a high-level group in the Biden Administration or in the Intelligence community, who convinced others that it would be a good idea with no tracebacks. Yes, I am open to the possibility that the Russians did it to themselves. I consider that somewhat less likely.]