I have had to use different programming languages for different tasks in my career- usually data analysis of large data sets...

I typically learn by looking up examples of code that are written to do things similar to whatever I am wanting to accomplish and write my code using those examples as a guide.

As a result I get an ugly patchwork of code that is inefficient and uses brute force to accomplish what I want. I don't really care if I get my answer in 10 seconds or 10ms... I don't care how efficient it is with memory, my only requirement is that it not crash my computer.

For any language getting to that level of skill is not terribly difficult. However, on some of my projects speed and efficiency of code is critical, I don't even attempt to do that code, I bring in professional programmers that have spent years learning the craft- That level of efficiency is a skill that takes a long time to develop, and requires learning more than just the language itself... there is no way I am going to get that skilled in my scarce free time.

I have written a lot of code in my time, probably all of it- outside of code I have written for a computer science class- is terrible in nearly every way, the only positive thing you can say about it is that it gets the job done.

Professional programmers do a LOT of work before they write the first line of code- mapping out in exquisite detail the best way to structure the program- that again takes significant education in computer science, not just the language in question. I am not, nor will I ever be, a professional programmer.

So if you want to learn a computer language well enough to accomplish a task- that is 'easy', if you want to learn a computer language well enough to do something with maximal efficiency- that takes a LOT of study.

There are lots of resources on the web to learn a language well enough to accomplish a given task- accomplishing that task with maximum efficiency, however- depending on the complexity of what you are trying to do- is something that I would say takes something akin to a formal education in computer science.