Since Zasttra is a marketplace (https://en.wikipedia.org/wiki/Online_marketplace), not an online shop, Sellers run their own store and you're buying directly from them.
Hence, the delivery time on Zasttra depends on the seller of the item.
The delivery method will depend on the seller of the item.
To see the delivery method, please go to the product page of the item you wish to purchase and then click on "SHIPPING & RETURN" tabs or simply click on "How long will it take?" on the products page.
To message the store owner: go to one of their product pages or their store page. In the sidebar, you'll see a green button that says "Contact Seller". Click that to send a message directly to them, and they will then reply directly to you.