Google Sheets – Keep Checkbox Value for Later Use

I'm working on a Google sheet actually (only for fun) and I'm actually stuck on something, as I said in the title, I want to keep a checkbox value in Google sheet.

I will explain my problem.

I'm doing a sheet of some information who will appear when I change the value of a dropdown list. But I want to be able to check a checkbox in one Dropdown item and when I change this item, have the checkbox who will take the value of the other item. A little example:

I have 2 dropdown item: one called poney and the other called horse, I check the checkbox while I was in poney and I change to the horse. I want the checkbox value go to false and when I go back to poney the checkbox retake the value true

EDIT: I add a Google sheet example on how I use it: https://docs.google.com/spreadsheets/d/1ySbHJJohneH_2hS3_lhl2Va-U4ejan-jeW0btbaMGlw/edit?usp=sharing

I hope someone can help me with that!