Connecting mikrotik lhg to UniFi sg

Hi, I’m having trouble getting the above setup.

I was told to try PPPOE so setup a PPPOE server in routeros on lhg and on the UniFi, tried connecting the wan interface using the protocol. Can’t get them to communicate though and I’m not getting a network connection.

Am I on the right tracks with this or should I be attempting this another way?

Thanks for any and all help offered