Pumpkin Stew

• 2 stalks celery coursely
• 1 onion coursely (chopped)
• 2,400 gr pumpkin
• 1,200 ml water
• 700 gr beef round (boneless)
• 200 gr green peas (frozen)
• 32 gr all-purpose flour sifted
• 14 gr butter margarine (not)
• 1 gr salt
• 1 gr thyme (dried)