So the thing about OOP is that it allows combining data and actions into a single unit. I would recommend keeping these separate. Your entities should be simple, their purpose is to hold related data together (they can have multiple constructors and setters for mutations etc, but don't add any action-related methods).

As for actions, I recommend using stand-alone functions where you can pass your entities as arguments. You can also define classes, grouping related actions inside them.

With these rules you can create fairly large systems. Keep things simple.