That doesn't look too bad. Assume the rot is on the external face? chuck some photos here of all of the damaged bits. Could be saveable, assuming you might want to try saving them.
It is saveable, as our surveyor said it can be repaired when the flat was looked at, but be good to replace the windows with a decent double glazing regardless.
Old wooden one in the front, the wood is rotten, windows can be repaired but would like to reduce noise from the road to zero (doable).
The rear is old PVC that still decent but nowhere near the standard of modern windows