だ、ダメかな？下の名前で呼んじゃ。

tbd

I-Is that OK? Calling you by your first name...

いやいや、結構結構。下の名前で呼び合うのは親近感がわいてよろしいことだ。

tbd

Not at all, that's perfectly fine. Calling each other by one's given name is a good thing; it produces a feeling of fellowship.