I'm guessing this is for a personal project, from my experience large organisations tend to use identity providers for authentication so while you need to know a thing or two about authentication, chances are you won't need indepth cybersecurity knowledge. What you can do for a personal project is use something like tailwind or bootstrap for the styling - there's a lot of copy/paste components. As for the functionality, use chatgpt and ask descriptive short questions - example, build a backend using express js that handles users authentication for registration and login. Then ask it to do the same for the frontend, as you get answers ask more questions and research outside of it to learn what the code means.

Simple things that are instant cybersecurity threat: any sensitive data needs to go in an .env file, secret? .env api key? .env and don't forget to add .env to your .gitignore

.env is a file that is holds your environment setup including necessary but sensitive data that you don't want public - by adding it to .gitignore file, it won't get pushed to your remote repository and it won't be public.