to understand
Je ne comprends pas ce que vous dites. I don't understand what you're saying.
mal comprendre to misunderstand
J'ai dû mal comprendre. I must have misunderstood.
Je la comprends mal, c'est à cause de son accent. I can't understand her, it's because of her accent.
se faire comprendre to make o.s. understood
(ses intentions)
to get one's ideas across
On peut le comprendre, mais cela n'excuse en rien son acte. You can understand him, but that's no excuse for what he did.
Sa femme ne le comprend pas. His wife doesn't understand him.