It’s best to upgrade your kitchen and dishes to their maximum capacity before joining the event- this increases your chance to make it on the leaderboard.
Having lots of boosts will greatly help you in overcoming all the game conditions in each restaurant.
You can purchase your boosts from the shop before playing in the event and use them wisely.
If your orders have piled up, use the grocery boost, and if a customer is about to leave, use the lollipop boost.
The pace of the game gets faster as you go along so make sure to keep up by preparing and serving the dishes as fast as you can.