Whatever interest you accrue while in forebearance will be added to the principle balance when you resume payments (capitalization).
From that point on, you will accrue interest on the principle and your monthly payment will first be applied to interest, then to principle. If you pay more than the minimum, you need to make sure it's being applied to principle and not pushing back the date of your next payment. All of this is per individual loan.
You may want to consider consolidating your loans, depending on your situation. You might be able to reduce that interest rate. There are various threads (including referral codes which get you money) about SoFi, but there are other companies as well.