I took differential calculus twice at two different colleges and it still took me at least another decade before I understood it. It is a simple subject but not the way it is taught.
Differential calculus is the study of one particular property of functions. So it is absolutely necessary that you clearly understand what functions are including graphical form, what it means that they have properties including point properties, and what some of their properties are before you go on to differential calculus.
The point property being studied in differential calculus is the slope (aka "rise" or "grade") of a function which is expressed as a different function of the same independent variable as the original.
Differential calculus is not about limits. The use of a limit is simply a device to enable us to formally obtain the derivative of a particular function. In practice only mathematicians use it. As an analogy, a gun is used by a holdup man but holdups are not about guns. In fact the slopes of a constant function and a linear function are clear without using a limit.
You'll learn the derivatives of the elementary functions, notation for the derivative, properties of the derivative, applications of derivatives, higher order derivatives, and why some functions don't have a derivative at some points or even at any point!
It is customary to teach differential calculus formally and abstractly which completely obfuscates the subject.
Integral calculus is the study of a different property of functions and it too is not about limits.