How to access column in another table through bridged table?

This is what relationship looks like:

They had many to many relationship but then I created a bridge table Calendar. I need to get number of orders placed the next day. This dax just works fine. TotalPatients =
VAR NextDateInNotifications = MAX('Notifications'[Nudge Date]) + 1
RETURN
CALCULATE(
COUNTROWS(
SUMMARIZE(
FILTER(
ALLSELECTED('Orders'),
'Orders'[OrderCreationDatetime] = NextDateInNotifications
),
'Orders'[CustomerID]
)
)
)

The problem is that I need to count all customers who placed order in a specific category. Now, categories are mentioned in Notification table and not in orders table. I am confused about how to incorporate this? So for instance currently it gives me these counts.For instance if notification was received on 18, and order was placed on 19 then I will get count for 18 like this:

But now I need to add category in it as well. Please guide.