I used Ubuntu before and now I migrated to Kubuntu. And I'd like to know if there are 'workspaces' in Kubuntu and how I can switch between them with shortcuts.
The only difference between Ubuntu and Kubuntu is that Ubuntu uses Unity as the Desktop Environment and Kubuntu uses KDE. Linux allows the user to choose which Desktop Environment to use, you can install Unity or Cinnamon or LXDE or whatever you want on your Kubuntu.
That said, yes indeed KDE (which is what you are using) offers workspaces. You should be able to control their behavior by going into the settings app (or running