Please i need help to know why the background image isn't showing

Question

https://code.sololearn.com/WhOHtSLz9Fpz/?ref=app

Answer 1

1) Download Dropbox
2) upload that phone to your Dropbox
3) copy the link that Dropbox give to you
4) paste it here

Answer 2

Please refer to this discussion on how to use images:

https://www.sololearn.com/Discuss/1054246/?ref=app

Answer 3

I don't understand