Yes, you can make your monthly payment in two installments. If you meet eligibility requirements, you can schedule two automatic recurring payments per month (more information here). If you are not eligible, or if you prefer to schedule them manually, you can make multiple payments manually every month, or schedule one automatic recurring payment per month plus as many manually scheduled payments as you like.
Automatic recurring payments will occur on the same day every month. Manually scheduled payments can occur on different days, depending on when you choose to schedule them.