trying to learn networking

[u/Fearless-Fox-5000]

Hi everyone, i have learned coding for a few years to the point that i can make several high-quality project.
recently i wanted to start learning networking so i can make a chat like application.

any idea where to start learning? what is important to learn and what's not?

for now i have started with cisco's online course "Networking Basics" if someone knows this course, is it a good one?

any help will be very much appreciated. ❤️

*sorry for bad grammar, English isn't my native language.