sometimes contribute pages on japanese and sino-xenic words to wiktionary. wiktionary surprisingly has a lot of gaps in its sino-xenic entries, often missing some very common words in the languages and/or failing to hyperlink sino-xenic words' cn and jp variants with each other.
PSA: remember, spend 5 years going through genki, japanesepod101, and duolingo japanese and make sure to spend at least 2 hours a day speaking with natives about how fun the o-shogatsu festival is and one day you'll be native level in the language. don't bother immersing with the culture either. hanging out with expats and watching shows with english subs all day every day is a-ok as long as you find some natives at your local roppongi bar and talk with them for 2 hours per day. After 5 years, you'll definitely be 準備万端 for the JLPT N3!
also forget learning kanji. you'll absorb the readings over time and will never mix similar ones up after a while. japanese only uses 1100 kanji anyway compared to chinese's massive 50000. and chinese knowledge won't help you at all with japanese, all the kanji have totally different pronounciations and don't line up with chinese pronunciations. like 手紙 is a letter in japanese but toilet paper in chinese, what's up with that?? and why is it tegami in japanese and showji in chinese? 私 is "me" in japanese but "private" in chinese? i don't get it...