Hallo Herr Kim!
Well there's a lot of korean chatting slangs, which makes its translation harder, anyway I'll try.
앜= Ahahaha; lol
저 아직 어리니까 편하게 (말해요)!
= Since I'm still young, so don't be too formal/polite! (Liberal translation)
= Since I'm still young, so (speak) casually! (literal translation)
거러고보니(X) => 그러고 보니(O) = come to think of it
넘넘(X) => 너무너무 = So/very. I don't think this adverb is really necessary in this sentence.
우리 동갑이네요? => We're the same age, (aren't we)?
*Additional Notes*
- I know it might sound weird, but age does matter when we're speaking in korean. (ex- 존댓말/반말, degree of politeness etc.)
- It's just my opinion, however, I wouldn't recommend you to learn korean with this partner unless you're an advanced learner, since ungrammatical slang & expressions like this will make you confused while you're learning. Just my opinion!