Only way drinking too much water will kill you is if you drink VERY much water and DON'T eat salt (or other minerals)
the two litre a day thing is an exaggeration , you get plenty of water by eating
on a normal day, drink when thirsty, if in the sun / working hard/ exercising, give yourself a buffer, as you get tirsty after starting to dehydrate.
Your urine should be transparent, if it is yellow, you are not drinking enough, if it is transparent, you are probably fine