If you're having trouble with a Waveshare display (screen showing lines or similar issues) it's usually due to configuration.
All of our Waveshare listings have a link to the official Waveshare setup guides within the product description over on the store website. Check your order history to find the product number/name.
Please ensure you've followed the setup exactly as per the instructions, including any changes made to Raspbian to ensure the screen functions as intended.