You can deactivate your offer by removing the offer hook or the stock for an offer.
You can deactivate all variants of a product collectively by going to Products in the shop backend, hovering the cursor over the corresponding product and using the deactivation button, as seen on the image.
You can also deactivate your offers via offer import. For this you have to enter the value "false" in the column "active". More about it: How do I deactivate an offer via the offer import?