We start physics...

OK physics I would like to say is a wonderful subject.
(Teachers who make physics boring are criminals -walter lewin)
So to begin I would strongly recommend that you ask questions like a baby does how, why, if and so on, it is the main thing that drives the world.
Let's begin by talking a bit on quantities.
What is a quantity? Well a quantity is anything that is there to tell about something.
We are mostly interested in physics in Physical Quantities. So a physical quantity is a quantity that you can measure. You cannot measure happiness right? So happiness is NOT a physical quantity.
There are two types of physical quantities we know, fundamental quantities and derived quantities. Fundamental quantities are there from the start, like mass, distance, time ....
Derived quantities are stuff that you get by playing around with fundamental quantities like speed, acceleration...
All these quantities have dimensions not the dimensions of 3D and 2D but dimensions of units.
How many dimensions does length have? One the dimension of length.
OK how many dimensions does velocity have( velocity=length/time)?
Acceleration? Force?(acceleration=velocity/time, force =mass* acceleration )
Try to find out objects with higher dimensions.