Making a large payment or additional payment on a Personal Loan will not automatically reduce your monthly payment. If you make a large or additional payment, the first part of the payment goes toward any interest accrued. The remainder goes toward the principal balance. That means even if you pre-pay in a given month, your monthly payment amount will stay the same and be due on the same day of each month.
After making a substantial payment you are welcome to contact us here and request to re-amortize your loan, which may bring your payment down.