Wash, clean and roughly grate the cucumber. Drain in a sieve. Put yoghurt and olive oil in a bowl. Peel 2 cloves of garlic and press them into the yoghurt. Season to taste with salt and pepper.
Wash and peel the potatoes, cut them into 3-4 mm thick slices and put them in water. Soak 2 slices of bread in cold water. Peel 1 onion, dice finely. Peel and finely chop 1 clove of garlic.
Wash oregano, dab dry and finely chop the leaves of 2 stems. Mix well the minced meat, egg, diced onion, squeezed bread, ketchup, chopped oregano and garlic. Season the mince with salt, pepper, paprika and cumin.
Form 12 oval bifteki (approx. 40 g each) from the mince. Heat 3 tablespoons of oil in a frying pan and fry the bifteki (possibly 2 x 6 pieces in a pan) on each side for 6-7 minutes at medium heat and keep warm.
Peel 1 onion and cut into cubes. Wash and cut the tomato into eighths and dice it. Heat 6 tablespoons of oil in a pan and fry the potato slices (in 2 portions) over medium heat on both sides until golden brown.
Remove potatoes from the fat and let them drip off briefly on kitchen paper. Season with salt. Stir cucumbers into the yoghurt and season again. Serve the bifteki with the potato slices and tzaziki and garnish with lemon, olives, diced tomatoes, onions and oregano.