In many languages, complex words abound. You can use the “breaking down and associating” method to help you.
For example: diligent.
What does this word mean to you? It means hardworking but to you – it’s just another word to memorize. But… What if…
You break down the word into 'dell agent'. Now, dell agent is more meaningful than a strange word. Now, you can associate a dell agent being hardworking when you visualize with your imagination this dell agent working hard at the computer.
There are thousands and thousands of words that you need to know. What's worse is that tests are testing on your vocabulary, and to have a wide range of vocabulary is by no means easy. But it can be if you take this advice and use the method introduced to you just now.