"The politician wants peace."
Translation:Der Politiker will Frieden.
"Die Politikerin will Frieden" is accepted already. You need to make sure to use the female version of the noun, not just change the article because "die Politiker" means "the politicians".
Der Politiker will Frieden = The politician wants peace (male)
Die Politikerin will Frieden = The politician wants peace (female)
Die Politiker wollen Frieden = The politicians want peace (male/male+female)
Die Politikerinnen wollen Frieden = The politicians want peace (female)
Die Politiker will Frieden = ungrammatical nonsense
Male and female variants
The grammatical gender usually matches the biological sex of the person you're referring to, i.e. the word that refers to a male baker is grammatically masculine, and the word that refers to a female baker is grammatically feminine. In the vast majority of cases, the female variant is formed by simply adding the suffix -in to the male variant, e.g. der Bäcker becomes die Bäckerin and der Schüler (the pupil) becomes die Schülerin.
The plural of the female variant is formed by adding the suffing -innen to the singular of the male variant, e.g. "die Bäckerinnen" and "die Schülerinnen".
Keep in mind that, in some cases, the plural comes with an umlauted stem vowel. This applies to the female variant as well, e.g. "der Koch" becomes "die Köche" and "die Köchin" becomes "die Köchinnen".
On this particular topic of Politics, there seems to be no rhyme or reason as to the use of "the" or not the use of "the" . When it doesn't state "der/die/das", or "the", I haven't put "the," and then it's marked wrong. Then in a similar example, I type "the," and it counts it wrong?! Can a native speaker please explain when you do or do not put "the" or "der/die/das/den" when the German does not have it in the sentence? Thank you for any help on this matter. (i.e.-- Politik ist wichtig." Translation: ? "Frauen haben Stimmen." Translation: ? )