Ist es als Soldat eigentlich verboten Gras anzubauen bei sich zuhause (ich meine ist ja nun schon länger legal)?

You can grow, but you don’t have much of it because you can’t smoke it. It would not be illegal, but consumption against the rule of service. Even Dutch soldiers, etc. may not be tricked. This is also relatively conclusive when handling weapons. It may be that the next day is still slightly foggy and not 100%. I can’t confirm this, but they’re taking it that way.