「邪魔してる?」 → Am I getting in your way? / Am I interrupting?
「邪魔してないよ」 → No, you're not getting in my way. / Of course you're not getting in my way. / Of course you're not interrupting.
ボキャブラリー
get in 人's way / interrupt = 邪魔する
of course you're not ~ = ~しているわけじゃない