Electronic charge is a fundamental physical parameter just like the speed of light, for example.
In the study of static electricity, there is the concept of 'Free Electrons'.
These are separate charges which move about without being bound to a nucleus. The charge is a magnitude only; it has no positive or negative per se, but with respect to the nucleus of an atom, the electronic charge is opposite to the charge of the protons in the nucleus.
It is important to remember that with moving electrons there is a current. The direction of the current is positive if one way into a terminal, or negative if the opposite way. You need to understand that with 'charge' and 'current', the charge is a magnitude only.
I have a beautiful old book called 'Principles of Electricity and Magnetism'. It was written in 1949 by Professor Harnwell of the Pennsylvania University. There are many other books too, but I have this one which I bought at a fair in 1978.
You might try to get a similar book.
Good luck with your study.
Hope you are satisfied with my answers.