How to properly size objects?

Question

Unity

I'm making a game like 3 in a row, I created a canvas (Canvas), placed a board (Panel) on it, I'm already displaying prefabs (cubes for moving) on ​​it for actions. Everything works, everything moves, disappears, appears, etc.
It's time to add some text, buttons, etc., and then there are problems:
1.) The text is huge (14px half screen).
2.) The canvas itself is ten times larger than the screen and it is not adjustable in size.
3.) Actually, because of this, I cannot scale the board itself.

Can you tell me how to set the correct dimensions in my situation?