Why not simply use separate text layers? Sounds like an odd approach to a simple problem.
I want them to be at the right distance like in the test layer
Clicking every time copy and paste isn't difficult either, but if you use these functions a lot, you prefer to use shortcuts to speed up the process
It's the same for me
I'm not sure I follow you. If you want two centered sentences then create a text area by clicking and dragging in comp panel with the text tool, start typing, set the paragraph style to centered and then make sure that the position and anchor point of the text layer are centered.
Another way is to use the keyboard shortcut Alt/Option + Ctrl/Cmnd + Shift + T to add a new text layer or just use the Layer menu and add a new text layer and the cursor will be centered in the comp panel providing you have not messed with the baseline. With the "centered" paragraph style applied you will have centered text.
With the latest build of AE you can add a position expression that calculates the area of a text field and then lines up that text field in the comp panel. If you want to get really fancy you can look at the size of a text field and offset vertically as well. I don't have time to write that expression for you but it's possible.