asus mother board and intel core i7 9700k processor and liquid cooler

Make sure to meet the seller in person and verify their identity. It is preferable to meet them in a public place with a friend present.

Make sure to inspect the product and have it checked by experts.

Document the sale/purchase process, including full details of the product.

Do not transfer any money until you have verified the following: (the seller's identity, the documentation of the sale, and receipt of the product).

Make sure to obtain a signed receipt from the seller.