It depends on what is causing the lines on your MacBook screen. Software and some hardware problems that cause lines on the screen can be fixed using built-in Mac tools and third-party apps. First, make sure your Mac doesn't get hotter than 192 degrees Fahrenheit, and set it to automatically cool down or slow down when it reaches that temperature. iStats Menu and AlDente Pro will help you with this. Also, run maintenance scripts (CleanMyMac X does this), reset the SMC, and run Apple Diagnostics. If you're using an external display, ensure the cable is tight and not worn, and the ports are not clogged. If the lines appear because the display has been damaged (due to a bump or a fall), it most likely needs to be replaced.