We have a hitron business line ( 200mb) . The software/firmware on the router is crap, the service only supports dynamic public IP and despite me fiddling with every configuration the router cannot forward ports .Do you need to enable modem only mode and use a second router to open ports ?
Give the Hitron a diffrent IP range from your network, for example is you leave it standard 192.168.0.1 give your network say 172.16.100.xxx
In the Mikrotik you just have to configure which ever port you have plugged the Hitron into, say Eth1 on the Mikrotik, then the Bridge and the reachable route. If you cannot do it yourself I would spend £100 or so on a person that can teach you. Well worth the money and you say goodbye to that odious Hitron.
Get a backup line as well, my Virgin line drops every couple of months.