Can you get a new graphics card for a laptop?

Not normally. To save space the graphic chip/card in a laptop is normally integrated into the system board and can't be removed or replaced. You are normally stuck with the video that you purchase in the laptop. There are some high end laptops which do allow you to upgrade the video components. But a $600 Lenovo is unlikely to be one of those units, They usually run in the $1500 to $2000 range.