Cocolutiion

Hi everyone so I just got a 2003 c240 from a private seller, well I just found out that my brake lights stay on even when I'm not pressing the brakes on the dash it says brake lamp visit workshop. First off I don't know much about electrical nor mercedes, I don't mind doing it myself since I love working on cars but since I don't know much of electrical in kinda stuck. I just replaced the driver side light bulb carrier since it seemed to be a little burnt for some reason but that didn't solve my brake lights staying on. Is there any ideas on what I should check to fix this issue I can't afford to take it in someplace right now so any ideas would be greatly appreciated thanks in advance