No. You may only take one class at a time. If you are in a hurry to complete two classes, once you finish the first class, then you can immediately begin the second. Once you complete the final exam in your first class, your teacher can enroll you in the second class.
ALL classes must be completed by the end of the term. Work does not roll over to the next semester. The latest students can enroll is typically 30 days from the last day of the term.