I assume that

I assume that is what I am to those gentlemen.

Je suppose que c'est ce que je suis pour ces messieurs.

— The Tale of The Princess Kaguya (2013)

I assume that you can speak French.

Je suppose que vous parlez français.

I assume that these documents are from your archives.

Je suppose que ces documents proviennent de vos archives.

— Three Colors: Blue (1993)

I assume that your mission was a success.

Je suppose que votre mission a été un succès.

I assume that this was Tom's idea.

Je suppose que c’était l’idée de Tom.

I assume that Tom doesn't know how to swim.

Je suppose que Tom ne sait pas nager.

I assume that's what you want.

Je suppose que c’est ce que vous voulez.

I assume that you already know the answer.

Je suppose que vous connaissez déjà la réponse.