This sort of stuff is enormously difficult to learn from books and unstructured on-line material. The problem, then, is that you need a properly structured course, with exercises and tests to help regulate your progress.
As others have said, you'll need algebra and trig, then you'll need some calculus. You need facility with word problems, and then some basic physics.
Here are some very, very simple basics to see where you are.
We can think of electricity as water flowing in a pipe. This analogy will get you a long way, but you will have to keep in mind that it is an analogy, and will sometimes be misleading. So ...
Loosely speaking, "Voltage" is the amount of "oomph" behind electrical current, it's like pressure. The more voltage you have, the more current you'll be able to push through a conductor.
However, a conductor will also resist the flow of current. In the simplest case, the amount of resistance remains constant over a wide range of conditions.
So, the formula is V=IR, (voltage drop across a resistor) is equal to (current flowing through it) times (value of the resistor).
The unit of voltage is the "volt"
The unit of current is the "amp" (short for "ampere")
The unit of resistance is the ohm.
So, suppose you have a resistor of 1K ohms (1000 ohms) and you put 2V (2 volts) across it. How much current will flow?
Suppose from A to B I have a resistor of 5K, and from B to C I have a resistor of 2K. If we have 5mA (5 milli-amps, 5/1000 amps) flowing from A to C, what is the total voltage drop from A to C?
Showing how you answer these will help us to provide suitable recommendations.
Finally, is there a local library? Is there a local college/university? Are you limited to on-line resources?