Some context might help, but in Baroque music the diagonal line between the A and the C would mean that you play F-A-B-C-F, as an arpeggiated chord but release the B immediately after striking it and hold the rest of the notes. Your final chord, there, dmin7, does not look like the last chord in a typical Baroque piece, so I'm not 100% sure.
It's the final chord in Beethoven's organ fugue. It is a D Major chord; the top staff is not a treble clef, but one (I forget the name) where C is the bottom line.
Soprano clef, with a C-clef thingy?
I don't what a thingy is, but it's just some clef indicating that C is the bottom line (where E is on the treble clef). But that is not important. What I want to know is what the diagonal lines mean and I think brogers70 is probably right.
But I don't think Beethoven made use of Baroque ornament symbols that were obsolete in his time. My guess would be that it indicates which "voice" leads to each set of two notes. Honestly though, I don't know.
Do you have any thoughts or reactions to Beethoven having used the C-clef (soprano)? This surprised a few of us.