I run out of time on lemon event before I reach level 25. What am I doing wrong?

https://sunny-house.fandom.com/wiki/Lemon_Event

Scroll down to 'Levels' it states that 21 is the highest level which is required to open Grandma's Workshop. This event is needed over & over to accumulate cash to use throughout the game. You can also farm energy. Each time playing, sell everything on the board that you can before the timer runs out. Full lemon trees earn more coins. I don't know how much cash is needed for the entire game. I haven't found that answer yet.