I have this thing that I really want the slurs to be heard in this beginning, not because it is something that gives a prize per se, but because it gives direction and gestik in German, it articulates the beauty of the phrases here.
You can try to do this legato all you want, but without using timing the listeners will never perceive the articulation the slurs indicate. That’s why I am quite free in this first part, but the freedom is structured, though. I think of the first beat of bar 2, 4, and 8 as “pillars’ and the notes in between are more “moving material”. As Leon Fleisher used to say in lessons: the long notes a little longer, and the short notes a little shorter. And within that, the engine inside is the harmony, how much gravitas there is towards a certain point.
I can’t stress enough: with legato alone, you’ll get nowhere. It will still sound note-by-note.
At bar 6 something very beautiful and quite soprano-ish happens when the melody doesn’t “land” but goes up (which makes it the common 2+2+4 pattern, which in itself has no value knowing). Very important to not be heavy on the first beat of that bar, but having almost a feeling of a singer going up, raising eyebrows…
There has to be a choice on which first beat is heavier: the first bar or second. As mentioned, I go with the second, it makes more sense to me in what follows, and the upbeat c going a full sixth makes the gesture more “up” than “down”.
As the piece continues, the pattern of reaching the main point in the two-bar phrases on the second bar is established throughout the first theme. But when the second theme enters in d-minor, the stress is on the first bar instead:
The two themes are so incredibly contrasting, also in their inner life: while the left hand creates nice “cushions” on the first beat in the bar for the first theme, the accompaniment figure (from the first movement) in the second theme is making it impossible to find any calm. It’s important to find that feeling of three voices, not top and bottom voice “bouncing” forth and back, but to mentally feel them as two different characters. Opera comes to my mind actually, with a lot of rhetoric gestures.
Finally, I would like to just mention the second part and it’s embellishments: Beethoven’s embellishments in the sonatas go from aria-like ones as in this movement to, in the last sonatas, being embellishments that are completely a part of the structure ( think of the variations on 109 and 111). But here, it’s more like in the baroque tradition that the same thing is repeated, this time with variations:
To be able to do this freely, it’s a very good thing to have played a lot of Mozart and why not J.P.E. Bach. But Mozart is even closer, though.