Learn Spanish (Latin America): El profesor habla alemán.

This is from the verb hablar (to speak). Because the subject is el profesor (he), we use the "he/she/it" form. For regular "-ar" verbs, you drop the "-ar" and add "-a", giving us habla.

Why isn't alemán capitalized?

In Spanish, the names of languages and nationalities are never capitalized unless they appear at the very beginning of a sentence.

Why is there an accent mark on alemán?

The accent mark shows you where to put the extra emphasis, or stress, when saying the word out loud. It tells you to stress the final syllable (ah-leh-MAHN). Without it, the standard rules of Spanish pronunciation would make you stress the middle syllable.

How would this sentence change if the teacher were a woman?

You would say La profesora habla alemán. The noun changes to profesora and the word for "the" changes to la. The verb habla stays exactly the same because it is still the "he/she/it" form.