As far as i know you can't delete orders. But it would be also the wrong way in my opinion.
If you delete the order you won't see e.g. wich campaign, product, at what time or what kind of device leads to the refund/canceld orders, You can't drill down in your data to see what causes you the damage.
In other words you will lost data wich is i,portant to make the right desicions.
Upload refund and canceld order, with the cost and all other data you have from backend and you can even dig deeper into the problems.