I can use variant for diferrent sizes but i cant figure out how i can effectively
You could use variants (assuming there aren’t hundreds!)
eg a margarita/margarita pizza would be normal margarita but a margarita/pepperoni would be half and half
We use something similar where the breakfast item is a choice of any two fillings eg:
The Loyverse app doesn't provide a feature to divide pizzas in half and select the flavours of each half.
Right now it's not to easy to track the ingredients for a pizza, perhaps you can just create an item specifically to be a half of a pizza, and assign to it modifiers.