Please help....

Here’s the scenario.
Previously mikrotik router was set up as a hotspot and dhcp server.
All port on 3,4,5 are bridged to br1. has ip 192.168.1.1
DHCP range is from 192.168.1.2-254
and is also configure as WAN load balance.

Now i bought a new fortigate to function as a firewall and vpn.
hence without wan on fortigate i can not create ipsec tunnel to the fortigate so i need to configure it as wan load balance instead of mikrotik and keep mikrotik to work as hotspot and dhcp server.
Fortigate now act as a gateway(192.168.1.2) for mikrotik hotspot.

How to configure mikrotik to route any other traffic which is not to 192.168.1.0/24 to gateway(Fortigate-192.168.1.2)?
What should i change in configuration in mikrotik?

Simplest approach would be to leave the Mikrotik as is; configure a /30 on the “WAN” interface of the Mikrotik to the “LAN” interface of the Fortigate.

Setup routing in between the two devices.

From there you can disable any firewall or vpn settings on the Mikrotik if they are not needed.

Can you provide a diagram and a bit more detail?