"I take them."
Translation:Ich nehme sie.
There is no word 'nimme' in German.
Maybe the conjugation table helps:
Conjugation is what you're doing when you modify the end of a verb (e.g. "to take") to match a certain pronoun (e.g. "he takes", but "you take"). In English there are usually only two or three conjugations for each verb. In German there are a couple more. They need to be memorised. You will eventually notice the patterns and common exceptions.
You can look up conjugations on various sites, such as Canoo.net.