It used to run good with lowest resolutions and now it dosent anymore should i check its temperature
A few things could account for that.
You should be monitoring temps for pretty much anything you game on, and you should be cleaning the case, fans, heat sinks on a regular basis. Get all that dust and such out of there.
Aside from those aspects, many online games are continually updating and can become a different challenge for the hardware it's running on. This is, of course, assuming you aren't talking about a game that doesn't update, etc.
It might be worthwhile to check to see that you are on the latest driver version, but honestly am not sure what the support landscape is on that card at this point.