I want buy a new monitor, but I have a doubt, I don't remember if the graphic card must be compatible with the monitor: in this pc I have an Nvidia 210 GeForce, will be compatible with a recent monitor ?
It's all about the connectors on the graphic card. Sometimes they'll be different DVI types: https://en.wikipedia.org/wiki/Digital_Visual_Interface Generally, there's not a lot of issues. But it'd help to know what connectors are on the card and what connectors are on the monitor model you're getting. Without that, no one can tell you anything.