Learn Hardcore Norwegian: Jeg forstår teksten nå.

Because it’s the first word of the sentence. In Norwegian you only capitalize the first word of a sentence (and proper names), so jeg would be lowercase if it appeared mid-sentence.

Why is forstår in its current form?

Forstår is the present‐tense form of the verb forstå (to understand). Norwegian doesn’t have a separate continuous tense, so the simple present covers both “I understand” and “I am understanding.”

Why isn’t there a preposition like “av” after forstår?

In Norwegian forstå is a transitive verb that takes a direct object. You say forstår teksten (understand the text) without adding any preposition.

What does the –en ending on teksten do?

The –en ending is the definite singular marker for common‐gender nouns. tekst (a text) becomes teksten (the text).

Could you say Jeg forstår nå teksten or Jeg forstår nå?

You could move nå before the object (Jeg forstår nå teksten), but it sounds less natural. Jeg forstår nå works if context makes it clear what you understand, but usually you specify the object.