Learn Swedish: Förstår du svårigheten? - Do you understand the difficulty?

It is built from the adjective svår, which means "difficult" or "hard". By adding the suffix -het, we turn it into the noun svårighet (difficulty).

How do we know to use -en at the end of svårigheten?

All nouns created with the -het suffix are reliably en-words. Because the sentence specifies "the difficulty" rather than "a difficulty", we add the standard -en ending to make it definite.

Does the verb förstår conjugate like the word står?

Yes! Just like "understand" in English, förstå is a compound word built on stå (to stand). Because of this, it follows the exact same irregular pattern as stå, which is why its present tense is förstår instead of taking a regular -ar or -er ending.

Why doesn't the sentence use a word for "do" at the beginning?

Swedish does not use a word like "do" as a helper verb to form questions. To ask a yes/no question, you simply invert the subject and the verb. Putting the main verb förstår at the very beginning of the sentence is all it takes to make it a question.