It’s legit but not complete, it’s not the official form (amtliche Fassung) and only the current laws, not the historic view. In Austria for instance RIS is much more complete: https://www.ris.bka.gv.at/

Edit: not directly related but a fun fact: in Switzerland you can get a copy of the constitutional laws for free at any bookstore and it’s supposed to be understandable for normal citizens and not only for lawyers.