Anonymous participant 442 Taiwan has being doing this since this year already.
Not knowing your overall background but
Just be patient and honest and supply the documents they asked for, write a good explanation letter attached to it. If you have something missing I’d suggest you explain as well.
In your case, the key is your income proof (freelance/FT job or even passive income - depends on your background), and your work proof.
Also it looks like thy have some doubt about your application so they ‘challenge’ you by checking if you’re being 100% honest.