How do you get an A or higher in the new star Guardian gamemode?

Me and my friend are trying to get an achievement where you need to get an overall rank A or higher. We kept on getting up to 4/7 S or higher out of the 7 "minigames" in the star guardian and kept getting an overall rank of B+ or B. Have any tips in getting an A as our overall rank?

Tell me If this makes sense to you or not.. xD