horizontal and vertical lines on the screen

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"—

https://www.apple.com/retail/geniusbar/

Outside the USA

https://locate.apple.com/country

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

Without seeing the issue, I would suspect a hardware issue. Take the laptop to Apple or an Apple Authorized Service Provider to be examined.