Hi Răzvan Alexandru
well, test with an external monitor /display to confirm the lines is on your laptop display.
you can try reaseating the LVDS cable and see if it helps.
what you are seeing line … most probably the lcd display bonding on your laptop display is not well bonded.
you can try stripping till you see the lcd module, and try applying light pressure to it.
sharing a video, fyi.
https://www.youtube.com/watch?v=UNf81Z-i1FE
imo the video is a short temp fix.