Most in the E70 section may know this already but I didn't so I figured this might help some newcomers to the site. I luckily paid attention to the fluid being "clear" in the power steering reservoir and then read the lid noticing it wasn't atf like my e53 uses.
So for anyone with power steering moans and such I made a video covering it (was bored today and made a bunch of them).
https://www.youtube.com/watch?v=TgZM7U979XU
I didn't film where I ended up going to autozone 30 miles away and buying the fluid. Seems its the same stuff used in most convertible power tops these days as hydraulic fluid. I know back when I had my audi it was a ROYAL pain finding this stuff outside of a vw dealership. Seems to be easier to get now.