The challenge when learning Japanese is the grammar, and grammatical system to express politeness and formality. Broadly speaking, there are three main politeness levels in spoken Japanese: the plain form (“kudaketa”), the simple polite form (“teinei”) and the advanced polite form (“keigo”).
Since most relationships are not equal in Japanese society, one person typically has a higher position. This position is determined by a variety of factors including job, age, experience, or even psychological state.
The person in the lower position is expected to use a polite form of speech, whereas the other might use a more plain form. Strangers will also speak to each other politely. Japanese children rarely use polite speech until their teens, at which point they are expected to begin speaking in a more adult manner.
Those two writing languages can be mastered but Kanji is much more challenging.
At Japanese language schools you can study Japanese from beginner level to advanced level. However many schools ask that beginners have at least a passive knowledge of Hiragana and Katakana when you start a long term course in Japan.