For current listings, if you are on the Seller Hub page, tick the little boxes left of the items scroll up to Actions>> Edit Best Offer.
Here is how to stop Best offers appearing on future listings. When you go to list your next item, do this,
after selecting Sell go top right of the page and select the business / advanced listing tool. Ignore that it says it’s for business and high-volume sellers only, it isn’t, it’s for everyone to use, and you will have far more control over your listings, and can de select that Best Offer option.
Use a desktop browser and not the app to manage this.
