well I have to agree there. I live in england and you'd think we'd be able to speak english pretty well. Some of the stuff that i hear come out of teens and kids mouths these days makes me wonder where the money we're spending on education is actually going.
Of course! The first frame is just fine. The second one is also fine. The third one: I would say "Because you're Batman" (we use "you're" instead of "you are" most of the time). I'd say "We know" instead of "we know it" because that also sounds more like regular speech. And "Bruce, you're no fun!" or "Bruce, you're never any fun" or even is probably how most of us would phrase the third sentence in that frame. Also, iff you wanted to say "We're going to bed" ("we're" instead of "we are"), that would sound fine.
Like I said, you did nothing wrong, but that's what more casual English sounds like
We use A LOT of contractions. I'm, you're, he's, it's, they're, shouldn't, couldn't, can't, won't, you'd - these are all just a few. The rule used to be that you should save contractions for conversational writing and use the full words for proper writing, but I think contractions are beginning to become normal everywhere.
I love language. I'm majoring in English in college, actually! I'm starting to learn a second language, too. I just took a semester of French. It's the most similar language to English, but it's still really hard! You're doing great!
It's only really small things really. To sound more 'realistic' in the second panel Batman would say, "Actually, I'm doing a scan of my wounds because-" Then in the next panel then smallest Robin (Tim Drake?) would say, "Because you're Batman..." Same panel the Robin on the left (Dick Grayson I would assume?) would say something along the lines of, "Bruce, You ruin all the fun." Finally, in the last panel it would be, again, more 'realistic' to contact, "we are going to bed" to, "we're going to bed." And Then Batman would say at the end, "... So this is a "selfie," cool." That's how I would have edited it In the future, assume that any native English speaker contracts his words. Example: we're (we are), don't (do not), won't (will not), you're (you are) etc... Hope this helps you!