Apple mice don't have the right mouse button, they always have. Windows switchers abhor it. And - let's be honest - that 'secondary click' also has practical applications under macOS. So back with it, because you can just activate and use the right mouse button in macOS, almost like in Windows.
In fact, the new mouse supplied with the iMac no longer has a visible button at all. Even a mouse wheel is missing. That's because this Magic Mouse has a touch-sensitive surface. Rubbing from top to bottom (and possibly left to right) activates things like scrolling. At the same time, it also applies that the mouse can detect exactly where your fingers rest on the mouse. And that fact is useful for quickly realizing a right mouse button. To do this, first click on the apple at the top right of the screen and then on System Preferences. Or click System Preferences (the gear) in the dock, just what you want. In the window that opens, double-click Mouse. Click - if necessary - in a new window on Point and click. Then toggle the option under Secondary click in. Right-handers naturally opt for this option Click on right side; left-handers can also choose the left side here. From now on you have (again) a functioning right mouse button.
It is also possible to secondary click without a right mouse button. In that case, click the mouse while holding down the Control key on the keyboard. That way you will see the same context menus appear as with the right click. However, it is - certainly for anyone who is also used to other operating systems - an extra action that takes a lot of getting used to. Yet - even when the right mouse button is switched on - you cannot completely avoid combining with keys while using the mouse. For example, under Windows it is possible to drag with the right mouse button. Then, when released, a context menu appears with the options copy and move. Dragging right doesn't work in macOS. No disaster: if you want to move one or more files, drag them to the desired destination while holding down the command button on the keyboard. Actually, that's the only mouse-key combination that you have to remember after activating the right mouse button.