In general there are a few points on where you can improve on.
As you already mentioned: The lags... I hope that was only the recording and not the whole game lol.
I would like to see a few more cuts. Make the video look more interessting. For example from 2.05 there is one cut till 3.48 and only 4 kills. And the cut you made there looks like its just 10 seconds missing. The rest of the time that you are not making a kill, we just see you steping around and looking at people through the walls.
And adding game sounds would be cool as well.