If we're talking what really happened with Katte and Fritz in the time they had, as opposed to what would have happened if they'd had more time, I agree with selenak: Fritz makes the first move, Katte the older and more experienced (and probably more sexually confident) leads thereafter, with the addendum that Fritz probably, especially as time goes on, has very definite opinions about what he wants and when he wants it. I see him as progressing quickly to being a pushy bottom, and eventually moving to a switch.

Incidentally, the author of Zeithain agrees: Fritz makes the first move signaling, in no uncertain terms, that he wants Katte to top (it's implicit rather than explicit, but I see no other way to read their body language).

young Fritz probably had fantasies about being properly seduced by an experienced older man anyway, fitting the erastes/eromenes set up, and Suhm fits all the criteria.

I don't know how far they went physically (maybe they did go all the way!), but I definitely get an erastes/eromenos vibe from those two. <3 And I kind of suspect Fritz thought of it in those terms too, Greek terminology and all.

Any input is welcome, not least because it seems a key event and it's still something of a puzzle what actually happened!

Indeed!

ETA: I forgot to add that my headcanon (which seems very likely) is that Fritz first got a proper gay sex talk from Keyserlingk, Upstanding Governor in Charge of Sleeping in the Crown Prince's Room and Keeping Him Away from Women Chaste.

"Chaste" also included the sin of masturbation, btw...which, if Fritz is listing Keyserlingk, who was appointed by Dad to keep him in line, as one of the people he most loved, and Keyserlingk was one of the beloved Rheinsberg crowd, ima go with "Keyserlingk let Fritz masturbate whenever he wanted and probably gave pointers."