Let's rewrite the question as follows (I think best in positives...):
! CA: "4 of us are liars"
AB: "6 of us are liars"
DC: "3 of us are liars"
BD: "5 of us are liars"
E: "3 of us are liars"
Now let's figure what we can initially:
A! B can't be truthful; being so would mean he's a liar, which would be contradictory
If BD were truthful, it would mean BD is the only truth-teller (even F would be a liar)
If CA were truthful, it would mean CA is one of two truth-tellers. A, B, D, C and E contradict CA, so if CA were truthful, the mysterious F would have to agree with CA
DC and E are either both truthful or both liars. If they are truthful, it would mean A, B, D and CA are liars so F must be truthful (and agree with DC and E)
From that I conclude multiple possibilities:
! If F says "3 of us are liars" then DC, E and F are truthful only.
If F says "4 of us are liars" then CA and F are truthful only.
If F says anything else, then BD is truthful only.
So...:
! F can say "3 of us are truth-tellers" (Truthies: DC, E, F; Liars: A, B, CD, A)
F can say "2 of us are truth-tellers" (Truthies: CA, F; Liars: A, B, D, C, E)
F can say anything else (Truthies: B;D; Liars: B, A, C, D, E, F)