Japanese language has three writing systems: Hiragana, Katakana and Kanji. Learning the first two is not challenging whereas learning Kanji is very difficult.
Hello Masoumeh. I am afraid that learning kanji is difficult, but the more you know, the easier it becomes. Around 80% of kanji are divisible into two parts: a part which relates to the meaning of the character, and a separate part which is related to the (Chinese) pronunciation of the character. For example, 持 has the Japanese reading of motsu, which means 'hold'. The left-hand side of the character, which is found in many other characters, derives from the character 手 meaning 'hand, so this tells you that 持 has something to do with the hand. The righthand side of the character, 寺, has the Chinese pronunciation of ji, and it so happens that 持 also has this Chinese pronunciation. Now compare this with the Japanese word for 'wait', 待つ (matsu). Here the left hand side is the same lefthand side as in 行 'go', and note that 'go' is an opposite of 'wait' -- this is what the lefthand side character indicates (something to do with movement). Unfortunately the Chinese reading of 待 is tai, and not something like ji. However, when reading or writing these characters, keeping in mind the two different parts and how they relate to the meanings or pronunciations is important. The characters for 'wait' and 'hold' look very similar to each other, but there is an important and instructive difference in the lefthand part of the character. Approximately 80% of Chinese charcaters work like this.
I found Remembering the Kanji to be a great learning tool for tackling kanji. However, the memory devices in the book end up being very complex as you have to remember the meaning of the components of the kanji, how those components are put together, what the actual meaning of the character is (not always directly related to the meaning of the components), and then additionally up to 7 different readings for each character.
If you are determined to learn to write each character by hand, then such a guide is probably necessary. However, having studied Japanese for more than a decade and living in Tokyo for 2 years, I found it to be more useful to focus on reading characters rather than writing them by hand. Most Japanese people use LINE or email to communicate these days, and it is not uncommon for a Japanese person to forget the writing of a character now and then even though he / she grew up in a Japanese environment. If you do not practice the writing on a daily basis, it is very likely that you will forget it before long as it does not come naturally to non-native speakers. Therefore, I would suggest to learn to recognize kanji by sight and memorize the main 2-3 readings of the kanji as that would be the quickest way to achieve daily fluency in the most common real-world situations.