For the first, I really thank you for carefully trying to understand me.minkyu_lee,
If I understand correctly, you want to know which is the right driver to download for you card, right?
In this case, I think x11/nvidia-driver should be the right one (Note: you can install these drivers from ports, there is no need to download them from vendors' site).
However, knowing which NVidia card you have would help.
I'll check it up. Thanks.