I am at an intermediate Japanese level. Been learning it for 2 years now. Can converse in non technical subjects as long as the speaker is speaking clear and not fast. I stumble a lot more trying to speak it than comprehending it. I've heard Japanese doesn't have plural for a while and it's sort of true. There is a word to make things plural. But, you would never use it for say I have multiple tvs, cars, etc. More like using it as Alice-tachi the tachi meaning plural, or Alice and her friends.

I've watched some kids that are bilingual. Mostly as a cute way to help my learning of Japanese. I don't think any of them have ever used the English plural. Even some who mixed some Japanese and English together.

One thing I did notice is bilingual kids rarely used I, and you. This is almost always dropped in Japanese and they tended to drop it in English too.

When I started Japanese there was a joke I was told. There are 100 ways to say I and you and you are not to use any of them. This is mostly true. Especially for you.