How to configure Buffalo WHR-HP G300 as main router?

Hello,after long time i"m finnaly flashed mine Bufallo WHR-HP G300 with LEDE,but now is another pain in
head,how to configure him for main using,i know how to clone MAC,because now ISP givin iternet by MAC via dhcp,tried variants but no success,router at this moment have this config
this config stands behind my first router MR3220,and all devices getting internet from WHR,but if i add some dns like google or ISP,in other words i something broken :smiley: :unamused: