I have a very good friend that is Japanese. She came to the USA as an exchange student years ago and now lives and works here. Her biggest problem is subject/verb agreement. That seems to be a big problem for many non-native English speakers.
Also, as a non-native English speaker you need to be watchful of leaving out words like "a", "an", and "be". That seems to confuse people.
In general, you do very well. I would be delighted to speak a second language as well as you do. In the future, if I see any big mistakes in your writing I will let you know.