Do not study calligraphy!
If your goal is to learn Japanese as fast as possible, don't study calligraphy.
Because almost inevitably you will end up deviating and studying ancient Chinese calligraphy, which has nothing to do with modern Japanese language.
In everything in life it is important to focus. Focus is to concentrate on the things that are important and avoid wasting time with unimportant things.
I have nothing against calligraphy. If you want to study calligraphy, whatever your reasons may be, go for it!
But if your goal is to study Japanese as fast as possible, calligraphy is a waste of time.
Learning how to write kana and kanji is not that difficult. Most textbooks on Japanese will teach you how to write hiragana and katakana.
Japanese schoolchildren use kanji dictionaries to learn how to write.
But now there are some sites that teach how to write Japanese kanji
But I have seen many people who study calligraphy and get completely off the track. They start studying ancient Chinese calligraphy which has nothing to do with modern Japanese.
Even though kanji came from China, after hundreds of years Japanese kanji became quite different than Chinese.
That is because Japan and China never made any agreements to keep kanji consistent. Kanji in Japan was adapted to the needs of the Japanese population and the Japanese language.
The way of writing kanji in Japan is different than China. You should not confuse them!
Another problem with calligraphy is cursive writing. People who study calligraphy seem to be obsessed with cursive writing.
The reality is: cursive writing is OBSOLETE! It is not used anymore in modern Japanese.
Cursive writing (行書 and 草書) is a kind of stenography.
It is just a technique to write fast. It was very useful until the 19th century, in a time where there were no voice recorders or typewriters, and everything needed to be written on paper by hand.
Even in the western world stenography was very popular, and most clerks were required to know it so they could take dictations from bosses.
But in the Meiji Era the Japanese government decided to declare 楷書 (regular writing) the official way of writing in Japan, with cursive to just be tolerated among the civilian population.
With the advent of recorders and typewriters, cursive writing became unnecessary. It is not taught at schools anymore and most Japanese people are unable to read or write in cursive.
Nobody cares about cursive anymore, it is not taught anywhere.... except in calligraphy courses.