Ulrike, it would help to have some details such as wild or farm raised. I've only cooked farm-raised pheasant which can be cooked like a free-range chicken breast. Wild birds take longer to cook. I hope you don't intend to feed a crowd, they're pretty small.
Thaw the pheasant and get rid of everything but the breasts.
If you wish you can make stock with the trimmings, except the offal. Defat and reduce it for a herb sauce.
Vacuum package the seasoned breasts and SV cook at 145F for 90 minutes. At that point give them a pinch to check for tenderness. If they are still quite solid keep cooking until done, maybe as much as another hour.