2GB of RAM and 20GB of diskspace, that’s not even enough to drive a simple test installation of Zammad. 4GB of RAM I would say is a minimum and you should at least give it 100GB of diskspace if your planning on running it for a while.
I’m going to see if I can set up a digital ocean vps next week (or do not know what I prefer). I noticed already during testing already that 2gb is too little (there was a delay of 10 minutes between telegram messages).