First request body with charset as UTF-8:
{"coupon":{"code":""},"delivery_address":{"address":{"lastname":"Lastname","name":"Name","phone":"464646464","city":"Berlin","city_slug":"berlin","country":"DE","street_name":"Poststraße","street_number":"2","zipcode":"10117","latitude":45.23234,"longitude":37.77234}},"general":{"restaurant_id":"7444"},"operation":"validate","sections":[{"id":"111378","items":[{"comments":"","id":"1281010","size":{"name":"normal","price":9.0},"quantity":1,"main_item":false,"sub_item":false},{"comments":"","id":"1281010","size":{"name":"normal","price":9.0},"quantity":1,"main_item":false,"sub_item":false}]}],"user_location":{"latitude":45.23234,"longitude":37.77234}}
Second try with Escaping chars:
{"coupon":{"code":""},"delivery_address":{"address":{"lastname":"Lastname","name":"Name","phone":"464646464","city":"Berlin","city_slug":"berlin","country":"DE","street_name":"Poststra\\u00DFe","street_number":"2","zipcode":"10117","latitude":45.23234,"longitude":37.77234}},"general":{"restaurant_id":"7444"},"operation":"validate","sections":[{"id":"111378","items":[{"comments":"","id":"1281010","size":{"name":"normal","price":9.0},"quantity":1,"main_item":false,"sub_item":false},{"comments":"","id":"1281010","size":{"name":"normal","price":9.0},"quantity":1,"main_item":false,"sub_item":false}]}],"user_location":{"latitude":45.23234,"longitude":37.77234}}
Always responce
{"errors": [{"cause": "", "error_message": "The object specified by the given parameters could not be found.", "error_code": "617"}]}