The best way to figure out the time signature is by listening to the middle part of a piece, where the music is 'in full flow'. There I hear a slow 1 2 3. (But not in the beginning.)
Your 3/4 is correct too, but the tempo would be rather fast (quarter note = 120) and the notation less clear to read, I think.
The key signature is not very clear, as always with Nils Frahm. One of the reasons why his pieces are so beautiful.
I could try with 5 #, G# minor, but we'll need a E# too. So perhaps 7 flats are better:
Acoustics are so weird and interesting! I'm stuck with this part. (It's about m 38 on your file). I hear the d# too (red circle).
But on the video he definitely doesn't play that note at that moment: watch his thumb and hammers on the piano.
I finished writing down all the notes. But now I have to figure out how to play the piece.
As you can see in the first measure: the c# has to be played with the right hand. It is exciting that at some places you can hear which hand has to be used!
I didn't make a decision yet about the time signature.
The piece is so beautiful 'beyond any time signature'! I mean, there is no clear beat at all.
Berduxa played at the BBC Proms in 2015