Hello, this is my first post and I'm no networking expert. I've tried to follow multiple guides that, in theory, addresses my problem with no results.
I will first make a general explanation on what i think is the problem and the steps followed to address this problem, and, if you need further information don't be afraid to ask!

So, I have a mikrotik router running routerOs 6.49.10 and a generic bridged router that only gives a pppoe connection to the mikrotik router, which handles this connection.
Currently, the mk router has 4 active interfaces. Interface 1 is connected to a network that i don't manage and links my desktop with the router ( so I can SSH it and webGUI). Interface 2 & 3 are connected to my server. Interface 4 is connected to the bridged router and manages the PPPoe-out client. I also have a bridge between ETH1, ETH2 and ETH3 so I can ssh into the server.

My problem is this: I've managed to make the public IP from the PPPoe client to point to the server so I can serve my content, but after configuring the DDNS (so i can point my domain to the DDNS, my public IP is not static) I noticed that the DDNS is not pointing to the PPPoe Public IP, its pointing to the Public IP the ETH1 is providing (ETH1 is a subnet that has access to Internet and provides my office with Internet connectoin through his own ISP) and sadly i have no clue why or how to change this.

As a newbie you'll see i didnt provide any IPs, networks etc because I'm not sure what exactly you will need, so feel free to ask, i will answer ASAP (eta 5 - 10 mins). If you need any more clarifications i will provide them as well. Thank you for your time.