Don't worry, it's quite normal to forget words when speaking foreign language. It's because of stress. It will happen more rarely if you converse more using that language, so you feel more confident.
If you look for new methods to learn vocabulary more efficiently here are my suggestions (some of them were mentioned earlier in the thread):
-you can try spaced repetition systems such as Anki or Memrise; as someone wrote before they are even more effective if you try to learn whole phrases with the new word, not only the word alone
-you should read books, but watching Tv, movies, series etc. is even better for start I guess because it's easier to memorize words if you can associate them with some memories, funny/interesting scenes etc. Btw in elementary school and high school most of the vocabulary I knew I learned from computer games ;)
-thematic dictionaries are not a bad idea, you can also try picture dictionaries
-if you can afford it and you are really determined to learn a language it's always worth visiting a country when the language is in use - you will learn a lot of vocabulary that is often used in every day life; to reduce costs of travelling and stay with local people (which is definitely better for your language than staying in a hotel) you can try Couchsurfing
You can also try this funny Polish game for learning vocabulary. Unfortunately for now it contains only words on beginner and intermediate level, but there are many languages avaible: https://babadum.com/
Practice, practice, practice!
Look for sentence patterns that you practice with different contents.
There remain some words that are really difficult to remember: think of a funny story that helps you to rmember the pronounciation, maybe there are words in Arab that have a similar sound.
I believe that the problem lies in your method of learning the new words. If you memorize a list of discreet out-of-context vocabularies, you will inevitably forget the bulk of them when you want to use them. That's how the brain works. You can go for the vocab books which offer thematic units. That is, all the new words in the unit are about the same topic. Or you can use techniques such as concept mapping to link similar words so they will linger for a longer time in your mind.
In case you need more professional help you can contact me. Please see my profile for further information.
When you learn a new English vocabulary, you should make a sentence with that vocabulary immediately.
I hope it could help you.