do I mix it with buff or deck tan?or do anyone have any good idea for a proper mix for late war german dark yellow?

Oh no anothere can of worms . Take a look at Mr Hobby H 403 . See if you like that .

I'd go with Tamiya or Model Master Dark Yellow, as long as the batch isn't too greenish. Of course, I still have a few bottles of Floquil Mud in my stash, which I've always favored.
Bear in mind that Dunkelgelb was produced in many factories, in different countries, under difficult conditions. In some cases, local paints were remixed to approximately match the German standard, and in other cases, old stocks of Tropen colors were reblended to match after the North African campaign ended. Tomas Chory's book reproduces four color chips of original Dunkelgelb, all slightly different, and two of them a bit greenish.
As for early vs late Dunkelglb (which I'm not sure is even a real distinction), paint stocks weren't always used in the order they were produced, and old paints were too expensive to discard. For instance, the Tiger tanks sent to North Africa in 1942-43 were painted in obsolete tropical colors from the 1941 scheme.
Bottom line, once you've added a layer of road dust, the original shade isn't all that important.