Bitcoin.de isn’t an exchange in the traditional sense. Instead it’s a mix of a peer to peer marketplace backed by their escrow service. Registering is relatively straightforward, and they enforce a two-stage login, and then further recommend using 2FA to secure your account. Once registered, you then need to verify your details with them by sending on various pieces of identification.
The exchange works by allowing you to lodge funds to your account, and then matching you with a corresponding seller.