Hi glo,
Are you sure you mean "bridge"? In network terms that means a layer 2 link, tap as opposed to tun. That is not recommended in general and is almost surely not going to do what you are trying to do.
My guess is that you are sitting at home, you want to redirect all your Internet traffic through a VPN server in Germany, and in turn have it redirect VPN traffic through yet another server in Spain.
What you want, if so, requires
policy routing on the DeutscheVPN to use EspañaVPN as default gateway for its VPN client network, and routing on EspañaVPN, and SNAT on EspañaVPN for the DeutscheVPN netblock.
Yes, it is a mess. No, iptables is only a small part of it (and there, only on EspañaVPN server.)
regards, rob0