If you're having issues with performance, there are three things you can do.

1), If you scroll wheel and click on the "Extended Options" menu and go to "View Distance Settings" and click on the "FPS" box, you can put the desired amount of FPS you'd like to get while playing this mission.

2), You can use a Headless client to save CPU performance or get a dedicated server to host the mission, or you can join one that is already being hosted.

3), Arma 3 is a very CPU demanding game. I don't care if you think you have a good computer. The truth is no PC is capable of running Arma 3 flawlessly. If you are having trouble running this mission, it is likely you are demanding too much from the game, or you do not have a good enough CPU to run this mission alone; this is a multiplayer mission with a lot of dynamics. Tinker with your settings and play around until you've found a comfortable balance of graphics and performance.

Hope it helps, and thanks for playing.