As hard as I try to listen, I can't understand what he is saying because his Japanese accent is too strong.
こんにちは。
ご質問ありがとうございます。
"As hard as I try to listen,"＝「どれだけ頑張って聞いても」
"I can't understand what he is saying"＝「彼が何を言っているか私には理解できない、」
"because his Japanese accent is too strong."＝「なぜかというと、彼の日本語訛りが強すぎて。」
ご参考になると幸いです。
アメリカ合衆国 
