I didn't understand.

Dictionary
Examples

I didn't understand why the moon had taken Estrellita away.	Je ne comprenais pas pourquoi la lune avait emporté Estrellita.
I didn't understand much of what they were talking about.	Je n'ai pas compris grand-chose de ce dont ils parlaient.
I didn't understand what you were trying to tell me.	Je n'ai pas compris ce que tu essayais de me dire.
I didn't understand much of what they were talking about.	Je n'ai pas compris grand-chose de ce dont elles parlaient.
I didn't understand because they spoke in a low voice.	Je ne compris pas car ils parlaient à voix basse.
He was vietnamese, so I didn't understand him all that much.	Il était Vietnamien, alors je ne l'ai pas bien compris.
Yes I didn't understand half of it until recently.	Oui Je n'en ai pas compris la moitié jusqu'à récemment.
I didn't understand much of what they were talking about.	Je n'ai pas compris grand-chose de ce qu'ils discutaient.
I didn't understand half of what he said.	Je n'ai pas compris la moitié de ce qu'il disait.
I didn't understand much of what they were talking about.	Je n'ai pas compris grand-chose de ce qu'elles discutaient.
I didn't understand when you gave me the chocolate.	Je n'ai pas compris quand tu m'as donné ce chocolat
I didn't understand half the words she was saying.	Je ne comprenais pas la moitié des mots qu'elle disait.
I didn't understand the plight of the penguin until just now.	Je ne comprenais pas la détresse du pingouin jusqu'à maintenant.
This time, I didn't understand what they talked about.	Cette fois, je n'ai pas compris ce dont ils ont discuté.
I didn't understand it before, but my powers... they went dormant.	Je l'avais pas compris avant, mais mes pouvoirs... Ils se sont éteints.
I didn't understand it. "One small step for man..."	Je n'ai pas compris. "Une petite étape pour l'homme..."
I didn't understand it, but you were right.	Je ne l'avais pas compris, mais vous aviez raison.
If I didn't understand that, I'd really lose him.	Si je n'avais pas compris ca, Je l'aurai vraiment perdu.
I didn't understand what that meant until today.	Je ne comprenais pas ce que ça voulait dire jusqu'à aujourd'hui.
I didn't understand anything of what you told me.	Je n'ai rien compris à tout ce que vous m'avez dit.