He talks about their dream of the farm but George really doesn’t want to because he didn’t really want to hurt Lennie. So he just shoots him because Lennie killed Curley’s wife. And he knew that if he didn’t it would have been worse if the other men had found him.
This is where Lennie has gone back to that place by the river after he has killed Curley’s wife. Lennie expects that George will give him hell. he asks George if George is not going to do it. George says that he will not, but Lennie really wants him to.
