I need an Interior Designer

We are in the process of building our first house. We need some help in designing the interior. We know what we want in-concept, but it is hard for us to explain / visualize, and implement. We need assistance with at least the following: 1. Understand and evolve our design ideas to a point where we can implement specific items. 2. Provide advice and suggestions for improvements to our ideas 3. Help with identifiying specific items (color of paint and window frames, material and color of flooring, color of baths, kitchen, etc. The house is about 400M2 with a 2-car garage, 4 bedrooms, 4 special purpose rooms (fitness, office, etc.), Kitchen, dinning, living rooms, and 4 bathrooms. The house is located in southern Germany so materials are limited to what is realistically available in this region. We are not looking for high-end, brand-name items. We want good quality, but not luxurious. We are looking for modern / urban country style that includes wood, stone, and wrought iron materials.