My English is so poor, I have no idea what you just said. Can you say it one more time slowly?
I have no clue what you just said to me. Could you repeat it, but more slowly this time?
自虐的に言うなら、次のような言い方ができますよ。
ーMy English is so poor, I have no idea what you just said. Can you say it one more time slowly?
「英語が下手すぎて今あなたが何て言ったか全くわからなかったよ。もう一度ゆっくり言ってくれない？」
ーI have no clue what you just said to me. Could you repeat it, but more slowly this time?
「今私に何て言ったか全然わからなかったよ。今回はもっとゆっくり、もう一度言ってくれないかな？」
ご参考まで！
カナダ 
