If you cancel your $5 monthly subscription, you will continue to have access to your downloaded courses until the end of your billing period. After that, the downloaded files will be automatically removed. However, your course progress will be saved, and you can still access and complete your courses online.
You can cancel your subscription anytime through the "Offline Purchases & Subscriptions" section in the Settings menu of the app.
If you have both a Lite Plan (one-time purchase) and an Unlimited Plan (subscription), canceling the Unlimited Plan will only remove courses downloaded under that plan. Courses downloaded with the Lite Plan will remain on your device/app until you choose to remove them.