You will find various local suppliers of clay in Germany such as Faber and Kolb. These two clay suppliers would probably be the easiest to get to from your location.
Depending on the size of your clay model you may have to use a foam base to the clay to take up some of the bulk to minimize weight. All industrial clays need to be heated to become pliable for ease of application so there are a lot of stages that need to be learnt.
As far as learning quickly that is a long term goal, it's not like a TV meal where you can stick it in a microwave and after a couple of minutes you can eat. Clay modeling is your make it from scratch meal, it takes time.
,like a TV meal...
