1) 翻譯：學好英語的訣竅是要有強烈的學習和練習意愿。

A strong willingness to learn and practice is the recipe for English fluency.

學好英語 --> English fluency; 強烈的學習和練習意愿注意分成分：強烈的意愿? <-- 學習和練習

2) Unsanitary living conditions are a recipe for the spread of disease.

3) 搭配：

[搭配]PHRASES

a recipe for disaster/success

導致災禍的原因；成功的訣竅

To live every day to the full is a recipe for happiness.

快樂的秘訣就是每天都活得充實。