ISP bridge and DSL AC68U (SOLVED)

Hi! I am having some headaches with setting up my Asus AC68U. ISP's modem/router here in Switzerland is very bad and I cannot access it's GUI (they have something they call online cockpit, which is shit), so I bought Asus. Now, we set the providers device as a bridge but I cannot access Asus GUI, for the life of me, to set it properly up.

I am not an expert in networking by far.