I want to woocs_currency_data_manipulation based on the number of items

As you can see we have some weird discount system on EUR (main currency) and when we change to USD we lost them, it happens when you add many similar items, so I want to apply a discount on checkout for USD depending on how many items were added and if it’s possible its total value, if you have more than 2 items it will be 10% off, if you have more than 3 items it will be 20% off, something like that, I found this https://currency-switcher.com/hook/woocs_currency_data_manipulation/ but it works globally without care about the number of items or its value.

I hope you can help out.

The page I need help with: [log in to see the link]