Please note my corrections above. Don't put a space before an exclamation mark. Don't put a space after opening quotation marks. Something in language is either correct/incorrect or right/wrong, not true/false. There's no need thank us in advance - thank us after we help you by adding the "Thanks" icon to any response you find useful.
Your question is incorrect. You need to say:
Are you going to tomorrow's online class? (Use this if the class is being offered only online.)
Are you going to [attend] tomorrow's class online? (Use this if the class can be attended in person or online.)