Making it an upright bike will likely open up the number of buyers who can ride that bike, being that small the buyers are limited.
As a rule of thumb for me I don't mess with anything under 23" c-t.
I've never been able to sell smaller size road bikes, 23" to 25" is king and the most sought after it seems. Larger bikes can be hit or miss. I've had more than one buyer show up with their own step ladder to test ride and buy a huge frame road bike. The last one sold to a guy not more than 5ft tall. Even with the seat dropped to the frame he could barely reach the pedals, yet he bought it for my asking price.
I had a 19" Raleigh Rampar a few years ago, pretty much on par with that Continental, I listed it for $25 and got no replies. I even tried to give it away and I got no replies. Under FREE items, I got complaints that the bike was too low end or too small.
I saved the wheels, junked the frame, and sold the small parts on fleabay.
I'd have thought that beggars wouldn't be so picky but I was wrong. They wanted a high end bike for free or they weren't interested.
The bad part was the bike was really clean, with nice tires and good brakes. It really needed nothing.
I gave up on CL and FB, nothing but a waste of time for bikes, 9 out of 10 emails are scammers or data miners, or flat out scammers. Maybe 1 in 500 are real buyers and those rarely have any money.
I had a later model Trek BMX bike that I didn't want, it came with a lot of bikes that I bought cheap at a sale. The Trek was an entry level BMX bike about 4 years old. I listed it for $50, got no replies, I lowered it to $25, and still nothing, 6 months went buy and nothing, I finally put it up for free.
I got a page long letter from some woman who told me she was interested in it but only if I could prove it was 'safe' for her kid. She went on to quote a bunch of legal statutes about liability. I deleted her email, pulled the wheels and cranks and crushed it with the backhoe. I used the wheels to build a yard cart.
That Continental looks pretty clean, I'd take it and hang some fenders on it, and a Suburban saddle and bars and list it for $350 and see what happens. Anyone who really wants it will make an offer if they won't pay $350. All the rest are just tire kickers wasting your time.