Hi,

For memorizing new words please use this site:

http://ankisrs.net/

https://ankiweb.net/shared/decks/

You can install Windows version or Andriod App for free, for ios device you have to pay to install it.

You can add your new words or downloud prpared decks from second links and enjoy memorizing new vocabulary.

I promise you it works.

Good Luck

I usually write it down and try to memorize how to spell it, and now I am tring to use the root to remember it.

It is useful and fun to read books in English, kindle is very helpful 

thanks for all your advices, I will try them 

I had that same problem in the past, but I realized that after I started reading books in English my vocabulary grew really fast. Of course it wasn't easy, but it sure was worth it. Because books are long and have lots of words that are repeatedly written, in the beginning you'll start highlighting lots of new vocabulary, but suddenly  you'll notice you saw that word before, until the day you'll look at it and know by heart what does it mean.

Repetition works fine for me, so I started reading books in English on my cell phone because the Google Play or Amazon Kindle apps have a free built in dictionary, so you don't need to stop reading to look at its translation on a physical dictionary. It helps a lot to improve vocabulary in my humble opinion... I even bought an e-reader for a better experience (with battery saving and less headaches too, too).

Give it a try, I'm sure you're not going to be disappointed.

Take care!

Disclosure:

Except for the fact I'm a user of the products may be mentioned in my response, I'm not affiliated to any of the companies behind them.

The idea of "flashcard" has been used by many people. Yet in the age of internet, instead of carrying a physical deck of cards, you can use apps on the mobile. There are a few products on the market. Your can google them.

Moreover, some apps offer not only plain flashcards. They can help to "hack" your brain. There're a few researches on how people can memorize quicker and keep the memory longer. Things like "spaced repetition" has been built into some of the flashcard apps. I personally have been using them to expand my Spanish vocab and find them very useful.

Last but not least, some apps try to keep you sticking to them so they kind of "gamify" the learning process. Take the app I'm using for example, I'm scored and given medals by how many practices I've finished and how many days in a row I'm using it. 

Your mileage may vary but your can give it a try.