Hi Mateusz,
Thanks for reaching out to us!
While you can share ticket capacity for multiple tickets on the same event, I’m not sure this will work with what you are describing. The multiday ticket would have no way of sharing capacity with two separate tickets and track for each individual day.
You would need to sell tickets for each day individually, and set a fixed number of tickets for each. I think there may be ways to create “bundles” if you are using WooCommerce for your payment system.
Let me know if you have any other questions.
Thanks,
Sky