Rear brake grinds (drum) – Malaguti F12

Hello, I have bought myself last a unbasked Malaguti F12 Phantom (2010). The scooter has no damage except the rear wheel brake, which is difficult to pull and has almost no effect. If I have the scooter on the main stand I see like the rear wheel brake fast again when I give gas. Does anyone know what this could be & is it dangerous to drive like that? Greeting