Bad luck. Read less. Check every word. There is no need to memorise. The word will appear again so you get a lot of chance to earn it. Memorising will give you a headache. This is exactly how I learned German. I just wrote the meaning in the book, so if I needed to check again, I looked back. Don't be ashamed of forgetting and learning again.You learn even better that way. Now I speak like a native.

"When I read books in a foreign language I can't understand every word, and if I try to search for every strange word it will take up a lot of time and become boring. I can't memorise all the meanings of those words. Sometimes it causes me a headache." Keep at it, and don't worry too much in the beginning. It will be slow going at first, but as you recognise the words and phrases you can infer the meaning from the context. Try to use your imagination to work out the meaning, then check the dictionary if you are really stuck.

“Whenever I read foreign books, it takes me so hard to understand every word and it’s becoming boring when I want to know their meaning as it takes me lots of time to look for it. I can’t memorise the meanings of each word. Sometimes, it gives me headache.” Learning a foreign language sometimes causes us headache but this is just a part of it. It’s not surprising to know your method of learning as many tend to do what you’re doing (including me). Don’t be dismayed if sometimes you don’t get the meaning of each word but rather keep on going. Good job, really! Good luck! :)