I'm actually Japanese, and English is definitely not spoken where I grew up. I learned it in the hard way as a second language, but I speak it fluently. Most of my classmates don't speak English very well and they're often amazed at my English level. However, I don't really like it when I'm watching YouTube and someone asks me if I can understand what they are saying. First, I don't want to be interrupted constantly. And second, what am I supposed to say? I don't want to seem so arrogant and blurt out "Of course I understand what they're saying." What really irks me is when they test me by asking me to translate what they say to Japanese. I just want to watch a YouTube video, not being tested by my roommates. I'm really annoyed and this really happens a lot! They would play an English song and ask me if I can understand. And I would simply say "no" to be "humble" and show them how annoyed I am. But they just wouldn't stop. I get constantly tested and challenged. Well, I'm not insecure or anything. I am fluent and I know it. I just don't want to deal with their stupid test anymore. Any advise would be appreciated.

You are not being challenged, they are wanting to know.

If you can understand, just say yes, tell them you worked hard to learn.

Next tell them, you are busy and will tell them about it later.

Be proud of your ability.

You are not being challenged, they are wanting to know.

If you can understand, just say yes, tell them you worked hard to learn.

Next tell them, you are busy and will tell them about it later.

Be proud of your ability.
Thank you.

Just say "Let me finish watching this and I'll tell you"
Not everyone is challenging you. Most people ask because they want to know. Share your knowledge, you are building bridges.