Hi, Um…I Just Finished the Front-End Development and requested the certificate. Now i want to know Which Challenge i should do next, because the next one on the list is Data Visualization and it asks for a project on Sass and react which i didn’t learn yet So any little help would be appreciated thanks 
I would suggest using the beta site. There might still be bugs, but it has way more content.
EDIT: Not on the beta site yet, but here are the react challenges: http://hysterical-amusement.surge.sh/