You can also use apps like memrise, anki or mosalingua. These show you flash cards of words to learn or you can preload your own. The app has a formula that predicts when you are just about to forget the word and so it asks you to look at it again. These gaps slowly get bigger as the word moves from your short term memory into your long term. I think it's the fastest way to learn vocabulary with the smallest amount of work.

The best way in my opinion is to use it in sentences and get as much examples as possible.

make word-lists

It helps if you break down these words into simple forms that you know. For instance, if you come across the word "indestructible" and you can't remember what it means, break it down into: [in] [destruct] [able] in = not destruct = destroy X (construct = build!) ible = able to so indestructible means that you're Not Able to Destroy it. It may seem like a complicated method that just makes it harder...but it works for me! And if you only memorize those suffixes (like in~, un~, trans~, bi~, uni~, ~able, ~ible, ~tion) then you'll be able to understand longer, more complex forms of words

There are many options: - a dictionary - google translate - ask an English teacher Practice the words many times to remember it.