Learning fundamentals doesn't mean you don't code as you learn, it just means you code to learn rather than code to finish a project. Coding to learn is deliberate practice and is the best way to learn fundamentals. Just learning whatever you need to get a specific project done means you will always have a lot of holes, likely you'd get more things done in the medium to long run by practicing and learning things properly from the beginning instead.
The goal isn't to code to finish the project and ignore any questionable code you've written because "it works".
It's to write a lot of code which is practice in the end. It's expected you'll be doing an ongoing combination of writing code and looking things up as you go, but you're not looking for the first working solution that you copy / paste and move on. The topics you end up researching will lead you to write good code if you put in the effort.
There's been plenty of examples of doing this where I spent hours going over a few functions because I wanted to make sure I was doing things nicely and the journey to go from the original version to the end version lead to learning a lot. That might have been reading through 5 pages worth of search results, skimming as many videos as I could find and maybe even asking an open question somewhere which yielded code examples written by people who have been working with the language for years.
You can then use all of that as input to guide your code. Through out the process I may have written a few versions and ultimately landed on 1 based on what feels good when using it, isn't too clever, easy to test, easy to understand, runs quickly, etc. Basically all of the properties that make code good.
