It will be a good idea to give an option to skip question and move to next problem if you are not sure about the current problem.
Also if there is an option to display some Hint like codecademy if you are stuck, that will be quite helpful.
Love the website though. Great Work. Thanks.
You can always work on any problem on the site at any time. There's no button to guide you to a specific next problem if you choose to skip, but you certainly can do it.