I don't know if it's possible to really know how you measure up in a general sense (only particular things you're good at). But on the bright side, everyone else is probably having the same problem. My advice is to focus on what you can do, rather than trying to know the unknowable:
Keep learning (always)
Keep trying to get the job done, even if you don't know everything about it
Try to enjoy what you do
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
I don't know if it's possible to really know how you measure up in a general sense (only particular things you're good at). But on the bright side, everyone else is probably having the same problem. My advice is to focus on what you can do, rather than trying to know the unknowable: