date calculation in pivot table to show products over agreed date?
 

hi all, am new to this forum so please bear with me.
I have the following query:
1)***** Build pivot to calculate things like:

-********* Average lead time per order type
-********* Average lead time per platform
-********* Orders breached SLA per month for the last six complete months.

2)***** Represent graphically:
a.****** Monthly order growth per customer
b.***** Current order status for those started in the last two months.

and not sure how to calculate dates in excel. I have the agreed SLA agreed date and days and also the order start and finish dates and orders?

I appreciate any help! and thank you for your time