That is quite low by today's standards. Even if the recommended requirements by Steam for this game only specify 2GB, the game is likely using more than that. Keep in mind also that on top of that you have to add additional overhead for the OS itself and other processes. This is most likely the issue, which is consistent with the freezing symptom you describe.
You can try enabling Zram to squeeze a little bit more performance out of your RAM, but don't push it too far either: