Ah yes, I cut out just the floor in my example so it only used the floor as a sample for filling the lines.
First, what version of PS do you have. Not all versions have the Edit > Content Aware Fill command.
If you do have the command, a window should pop up showing the areas you are going to fill and the color overlay shows the sampling areas. You need to erase all sampling areas that are not specifically the floor (e.g. the white above the floor). It was most likely sampling the white areas of the image when doing the fill.
Give that a try. If still having difficulties and can post cut and pastes of the step by step using the whole image if that helps