Websites for learning English vocabulary

Hello! Aside from learning my usual German vocabulary, I have also started to review rare English words --the kind of words that native speakers can be aware of, but are tricky to bilinguals. And I came along a problem: I do not have the resources for contextual input.

What are effective ways to learn vocabulary? Can someone advise a website that does the job like Quizlet?

I usually use Quizlet.com for my German vocabulary and is good enough. It emphasizes words that I have trouble with (which is important to me), asks me to type, along with other functions. 

First, what I call contextual input is, for example, a unit in a book, a video, or a text that goes through a topic, in which words are repeated because of a specific context. I have a book with a unit on "inmigration" in German, for example, that helps me learn related vocabulary by using it frequently during the unit: in passages, grammar exercises, and others. I also use flashcards to aid me in the process.

But I learn English in a more passive manner. I lack the resources for advanced English vocabulary (like book units for example). Jamming words into my head using only Quizlet.com is not an option for rare words. I turned to this other website called Vocabulary.com, that has an array of flashcard sets ready for the go, and somewhat also provides context, which is cool. However, is not enough for me to have "some context", and I would like to have more contextual input without much hassle.

So I was wondering if anyone had a good experience with advanced English that would like to give me some advice on how to learn, or any tips. Or maybe I am being too demanding on my language learning experience and should do more research? Who knows.

Also, how do you guys learn vocabulary? Does your process look similar to mine? 

What do you think about this concept of contextual input? I took it from a Youtube video and applied it to vocabulary.  

 I do advise taking a look at the websites I mentioned because they are actually pretty neat. 

Greetings!

I will probably look into more specialized academic texts that go beyond my career. I have been into Physics and IT a bit too long and cannot get much more vocabulary out of it. 

Thanks, I kinda needed someone to ground me on the topic. And it's good to know vocabulary.com is already good enough for most people. 

I wrote a post about learning vocabulary here, but I've changed a bit since then. I still think one needs to be well rounded in their learning, but I feel I get more from exposure and using the reading tool. I recommend spending some time with it because it's great for actually assimilating vocabulary. And you can export the words you had to look up to an SRS, or just study them by themselves if you want.