Due to the Japanese population's decline, the domestic market will continue to shrink.
Therefore, it is necessary to have people who can speak English (which is a universal language), in order to increase the Japanese power in international competition.
ご質問ありがとうございます。
"Due to the Japanese population's decline,"＝「日本人の人口減少により」
"the domestic market will continue to shrink."＝「国内マーケットはしぼみ続ける。」
"Therefore, it is necessary to have people who can speak English"＝「従って、英語が話せる人材が必要である」
"(which is a universal language),"＝「世界共通の言語である」
"in order to increase the Japanese power in international competition."＝「国際競争で日本人の力を向上させるために。」
ご参考までに。
アメリカ合衆国 
