"Is it that you understand ?" => "Est ce que c'est ça/cela que vous comprenez ?" ("that translated to "ça/cela" is the point of interest in the question) "Do you understand ?" => "Comprenez-vous ?" ou bien "Est-ce que vous comprenez ?" ("understand" here is the point of interest in the question
You don’t need the “Est-ce que.” It’s just another way that you can say it, and you’ll notice that “vous comprenez" is still in there. You won’t advance if you keep learning the same thing. Previous lessons suggest less advanced learning and graduates to more complex as you continue. I promise you that it’s not required that you say “Est-ce que” unless it’s your choice.