how to improve speaking after N1

I recently took N1 exam and I’m very confident that I will pass with high score. But as a Chinese native speaker, I know that passing N1 itself doesn’t mean mastery of this language since I can just guess the reading/vocab meaning without actually knowing the words.

I can’t really speak or write Japanese properly (like I can express myself, but not in a well-structured way nor for more complex topics) , and I’m living in an English-speaking country where is a bit difficult to find an immersive language environment. What is advice moving forward? How can I improve my speaking if not using Japanese on a day-to-day basis?

Edit: I don’t have a plan to live/work in Japan in the foreseeable future; just want to improve from a pure hobby perspective