When am i going to use en or le le l' and les

Bonjour Naime,

You use le, la, l', or les when replacing a direct object (a noun with no preposition in front). You need en when the noun is preceded by de.

See lesson https://progress.lawlessfrench.com/revision/grammar/the-adverbial-pronoun-en-can-replace-a-phrase-introduced-by-de

For example,