It was very hard to keep track of which table of customers had eaten up to which part of the course menu and then to serve the right dish.
ご質問ありがとうございます。
"It was very hard to keep track"＝「把握しているのがとても大変でした」
"of which table of customers had eaten up to which part of the course menu"＝「どのテーブルの客がコース料理のどこまで食べたかを」
"and then to serve the right dish."＝「そして正しい料理を提供することが。」
ご参考に。
アメリカ合衆国 
