Chop the cucumber with a grater (medium size) and place in a prepared bowl with a sieve and cloth.
Salt and let stand while draining. Take the cloth and squeeze as well as possible.
Put the squeezed cucumber in a bowl and add the crushed garlic, Greek yogurt, sour cream, salt, pepper and lemon juice and stir.
Leave to stand in the refrigerator for a short time, arrange and garnish with stoned black olives to taste, if desired, and serve.