I bought it second hand and tried to run it a few days ago and it didn't even post 🙁. thanks for your attention thoughPlease make sure your graphics drivers are up to date first!
First: Use Heaven Benchmark or any benchmark and run it to get a score of your GPU. Then compare that score to online scores people have posted themselves. If the scores are close then this is probably a reporting error and you're fine. (I searched around you should be getting around 1500 points on 1080p extreme preset in heaven benchmark)
Second: If your scores are lower; since when have you owned this card? where did you buy it from?