By giving a quick look to the entire conversation, I agree with
@k.h.p.
Your file is not very weak, honestly. You do seem to have finances enough for a 15 days trip.
But being single is always seen as a risk of overstaying as person does not have a family he/she compelled to return to.
Family ties is important and what generally VO sees as a family tie is spouse and/or children, unfortunately, not parents.
What was your original purpose of travel? What did you provide in that?