Finishing someone else's project is definitely a challenge.
I discovered how much of one it could be when I undertook finishing a mystery quilt that had been started by someone in the beginning stages of Alzheimer's.
First I had to determine what it was supposed to look like as we had no idea where the instructions had disappeared to. Then take out all the mispositioned pieces and restitch 75% of it.
So I can certainly feel for you!
Took me a couple of months. Hope yours goes ever so much faster.