How to fix green line on screen

@usmanjaved39873 we don't know what this green line looks like. Could be a bad connector, bad flex or a bad display. I suggest you start with your display. Samsung Galaxy Note20 Ultra Screen Replacement

Oh yeah, post some pictures of what your screen shows, with your Question. That way we can see what you see.

Adding images to an existing question

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.