Why is my screen glitching with green lines and not starting up?

Hello,

My MacBook Pro is not starting up very well: it goes into the starting up screen (filled with green lines), shows a stripe of something like a test screen with all those colours, goes black for a second and turns completely white. It doesn't do anything after that.

My husband has installed better memory in my MacBook around half a year ago, and it's been glitching sometimes since then. It used to go away for a day or so if I restarted my device, but now it isn't starting up anymore. It would be awesome if someone could help me with this!