How to remove black horizontal lines appearing on the screen of MacBook Pro

It's possible that your MacBook Pro is experiencing a hardware issue with the display or the graphics card. The black lines on the screen could be caused by a variety of factors, such as a loose connection or a malfunctioning component.

To troubleshoot the issue, you can try a few steps:

1. Reset the PRAM and SMC. This can help resolve some display issues. Here's how to do it:

- Shut down your MacBook Pro.

- Hold down the Command + Option + P + R keys together.

- Turn on your MacBook Pro and keep holding the keys until you hear the startup sound twice.

- Release the keys and let your MacBook Pro start up normally.

2. Boot your MacBook Pro in safe mode. This will load only the basic system files and drivers, which can help determine if the issue is software-related. Here's how to do it:

- Shut down your MacBook Pro.

- Press the power button to turn on your MacBook Pro.

- Immediately hold down the Shift key.

- Release the Shift key when you see the Apple logo.

3. Connect your MacBook Pro to an external display. This can help determine if the issue is with the display or the graphics card. If the external display works fine, then the problem is likely with the MacBook Pro's display. If the external display also shows the black lines, then the issue may be with the graphics card.

If none of these steps resolve the issue, it's recommended to take your MacBook Pro to an authorized Apple service provider or Apple store for further diagnosis and repair.