Hi,
I have internet connection, 100MB, it is assigned a public ip, it is shared in 10 peoples, 1 of them is want to use ddns with public IP, I have done many tactics, but eventually while accessing public ip on browser it browse my mikrotik router, is there any way that while accessing public ip it can be forwarded to specific user's router rather than my mikrotik?

So you have one public IP.
Is your LAN, shared amongst the 10 people via 10 different VLANs??
Do you load balance between the 10 vlans???

So the person wants to do port forwarding to a server on his Subnet and he wants folks using his server to be able to use a dyndns name ??
Why not use the DDNS that is on the router itself, and then give him the domain name of it....
Its usually long and ugly ex.
62f30c89t1977.sq.mynetname.net

Then on his/her dydns provider all they have to do is link to that domain name.......via CNAME entry, and he will have linked his dydns domain name to the routers.
That should work........... Most people dont want to use the ugly name above and have much shorter easier to rememeber ones.

Then you need to setup port forwarding. Remember to ensure his vlan is segemented from others.
I would even suggest putting his server on its own VLAN such that if the server gets infected somehow it doesnt trash his other devices.