I fear that you have not made things more clear.
You have a modem from your ISP.
This modem/router is in bridge mode, and your WAN IP address 177.204.0.93 is an interface on the Mikrotik.
The modem/router is also broadcasting a WiFi network for you.
The Mikrotik is also broadcasting a WiFi network.
When a user connects to the WiFi network being broadcast by the Mikrotik you want them to be greeted by a hotspot login page, with a link that will direct them to a site running on your local server and you wish for users to be able to browse your server without the need for authentication.
It seems that at this point, you've addressed you're previous port forwarding and have questions regarding allowing access to a specific resource prior to login, and to customise the hotspot login page.
To allow the user to access your server without logging into the hotspot, please look at
https://wiki.mikrotik.com/wiki/Manual:I ... led_Garden
To customise your hotspot login page, please look at
https://wiki.mikrotik.com/wiki/Manual:C ... omizations
If I am mistaken and you're still trying to get something off the ground without and aren't sure how to go about it, why don't you give us an overview of what you're trying to achieve.