Oil light comes in only when I use the brake . What does that mean?

Hello, it seems like it's due to the engine speed decreasing and oil pressure decreasing at the same time. You'll need to have an oil pressure test performed for the engine -- with a manual gauge. Then you'll know if the oil pressure is sufficient or if there is a problem. If there is sufficient pressure, it could be that the oil pressure sending unit switch or wiring could be at fault. Good luck. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops