I want to combine 2 internet speed

Good Day,

Thank you for using the Community Forum. 

Link aggregation would help only in a LAN scenario, not the WAN. Link aggregation does not mean Bandwidth aggregation of Multiple ISP. It is used to increase the Port Density/redundancy, not the Bandwidth. 

- It is recommended to configure SD-WAN to load balance and utilize both the wan interface bandwidth efficiently.
- To configure SD-WAN, your wan1 interface references should be removed at first.
 > ISP technology cannot be combined and we cannot send a few packets via WAN1 and a few packets via WAN2.
> We can do load share with the number of sessions.
> The Below example explains how to do load sharing can be done in FortiGate.

> ISP 1 with 100 Mbps used by 10 users which will be around 10 Mbps each.
> If you add another WAN link with 100 Mbps bandwidth then each user will get around 20 Mbps.
> In the speed test you can't get a value of 200 Mbps but FortiGate will send 1 session to 1 ISP and the next session by the user to another ISP.
> Complete session will be shared equally between two WAN links.
> Speed test will result in data transfer rate and if you initiate the test it is one session and handled by one ISP only.

Ref:

https://docs.fortinet.com/document/fortigate/6.0.0/cookbook/990932/redundant-internet-with-sd-wan

https://www.fortinet.com/resources/cyberglossary/what-is-wan-aggregation

Thanks,
Feroz