You did really well! The only things I see really would be to make your imag responsive, which you can do by adding max-widtth: 100%; to your img class in css, that way it will never be bigger than 100% of the screen size. Also for your caption under the picture, checkout captioning in bootstrap to see how its done https://v4-alpha.getbootstrap.com/content/figures/
You’re off to a great start though 