Learn French: Après avoir fouillé la maison, l'inspecteur a tout compris. - After searching the house, the inspector understood everything.

In French, the preposition après must always be followed by the past infinitive, which is made of the infinitive avoir or être plus a past participle. It can never take a present participle (the -ant form). While English prefers "After searching," the literal French structure is "After having searched."

Why do we use the infinitive avoir instead of conjugating it, like Après il a fouillé?

Because the same person (the inspector) performs both actions, French prefers to use an infinitive phrase for the first action. Using après avoir fouillé is much more natural and concise than using a fully conjugated clause like Après qu'il a fouillé.

Why is tout placed in the middle of a compris instead of at the end?

When the pronoun tout (meaning "everything") is the direct object in a compound tense like the passé composé, it is placed between the auxiliary verb (a) and the past participle (compris). Saying il a compris tout is grammatically incorrect in French.

Could I use cherché instead of fouillé in this sentence?