Can we have some context for the question?
In general, If you're talking about graphically, that would be a local GPU, memory, or CPU issue with a game that has not been optimized. Your network connection to a server can have an effect on your gameplay as well. Until it has been fully optimized, I recommend throttling back some of your settings. Even with a decent rig, it can slow down in graphically intense areas (like horde night with a ton of zombies on screen). I use the command "GFX PP enable 0" on horde nights to squeeze every last frame I can. Then I disable it on normal days. Turn off reflections and other unneeded effects. Drop your resolution down if needed as well. I run on a 4K monitor but run 1080p instead.