Thank you...So they use every small words in their kanji form?even if they wanna write Sth very quickly?
You are assuming kanji can't be written quickly because
you can't write them quickly.
You are also probably assuming that everyone writes every stroke of every character and tries to write clearly. This is not how things are at all. People use many shortcuts when they are writing by hand. I don't know if you have had a chance to see much handwritten Japanese, but it can be very difficult for foreigners to read because we are used to learning from neatly printed fonts.
I am attaching images of some hastily scribbled notes on documents I had at work in the past couple of weeks. I took photos because I thought they were very good examples of how Japanese people rapidly write kanji when they don't have time to write more clearly. The kanji in them aren't difficult at all, but I suspect many foreign learners would have trouble recognizing them, especially without any context.
Also, people have their own individual habits and widely varying degrees of familiarity with kanji. Just because a person is Japanese doesn't mean their DNA gives them magical kanji powers. Lots of Japanese people struggle with kanji and have an inadequate knowledge of them. Many Japanese find kanji just as difficult as you do. The advantages they have are that they are native speakers of the language, that they have far far far more exposure to it, and they have to be functional in a country where kanji are
everywhere. Foreign learners will never be the first one, will find it almost impossible to catch up on the second one, and in many cases just choose to go through life in Japan essentially illiterate when it comes to the third one... they just excuse themselves from literacy.
