First off, awesome, well done! If you feel you need to follow a curriculum I can recommend Bookshark (if you can afford it). At this young age though it really is just important for your child to have fun while learning what they can. Maths, reading and writing can be learned through workbooks such as;
As for language learning, have you looked at Little Pim? There’s actually a Japanese episode on Amazon Prime TV right now!
Good luck, and don’t stress too much, it’s a constant process of finding what works and what doesn’t, you take it day by day.