Suppose I play this section on a piano.
Should C4 be pressed down 2 separate times?
Or should I just hold it until the end (pressing keys C4GAC5, then ONLY F)?
Thanks a lot!
Both the Ab and the C stay held for the whole bar. The G changes to F half way through.The top C is held for only 3 beats, but since it's the top voice, with up tail, it really needs a crotchet rest after the second chord. A tie will only join two (or more) notes that are the same. So it won't join anything except the two Cs. Afraid it's not very well written at all!
The OP's notation seems to be based on what was in the first edition, which apparently has a couple of typos in that bar - the Ab whole note is in a strange place, and the top C at the start of the bar doesn't have a dot.
It has always been a challenge for engravers to lay out keyboard music of this complexity so it is "easy to read", and different publishers often come up with different solutions. Also note the variety of "creative interpretations" added to Chopin's simple directions of "pp" and "Poco rall"!
IMSLP is a great resource for comparing different editions of standard works like this - unless you are required to use a specified edition for an exam or a competition, look at everything available and make up your own mind how you want to play the piece.