Question

Did I get this right? If not could someone explain this to me?

Answer 1

That is correct and good job on writing out what a independent and dependant variable is.

Answer 2

Correct!
Your notes on the right side are correct, too.

Independent -- not dependent on another variable
Dependent -- dependent on another variable

The height of the plant varies because/due to of the quality/quantity of fertilizer.
So, the height is changed by the fertilizer.

Thus: height is dependent and fertilizer amount is independent.