Why is there a black spot on right corner of screen and some lines?

First of all, your screen is damaged and will need to be replaced. You can follow this guide for a DIY repair.

More importantly, your phone has sustained liquid damage. Not only does rice not do anything to help this condition, it actually makes it worse. Because your phone is still “working”, you probably don’t have a lot of liquid inside but if you do nothing to address the issue, you run the risk of having issues later on. I would do the following:

• Open your phone and remove the logic board (follow this guide)
• Inspect the logic board, especially around the connectors and look for corrosion.
• Inspect both sides of the board. Unfortunately, most of the board is covered in shields. That's usually where the damage is occurring. You can peel away the black cloth shields on the back of the logic board for a proper look.
• Put your board in a container with >90% isopropyl alcohol and let it sit for a while.
• Use a soft brush, like a toothbrush and lightly brush away any corrosion you see.
• Rinse in alcohol and repeat.
• Let it air dry for a day.
• Re-assemble and hope for the best.