Learn Hardcore German: Morgen beginnt ein wichtiger Kurs an der Universität. - Tomorrow an important course begins at the university.

Here Morgen is a temporal adverb meaning “tomorrow.” You can tell it isn’t the noun Morgen (“morning”) because it appears without an article and directly modifies the verb beginnt. If you wanted to say “in the morning,” you would use am Morgen or heute Morgen, not just Morgen.

Why is beginnt in the second position, even though Morgen is not the subject?

German main clauses follow the verb-second (V2) rule: the finite verb must be the second element. Since Morgen (the time adverb) occupies the first position, beginnt must come next, and the subject ein wichtiger Kurs follows after that.

Why does wichtig take the ending -er in ein wichtiger Kurs?

Kurs is a masculine noun and here it’s the subject, so it’s in the nominative case. After the indefinite article ein, adjectives in the masculine nominative singular take the -er ending. Hence ein wichtiger Kurs. If it were an object (accusative), you would say einen wichtigen Kurs instead.

Why do we use an der Universität instead of in der Universität or no article, as in English “at university”?

An is the typical preposition for events or roles associated with institutions (e.g. an der Uni studieren, an einem Kurs teilnehmen).
It takes the dative when showing location: an + der (feminine).
In der Universität would emphasize being physically inside the building.
Unlike English “at university,” German requires the article—so you cannot drop it.

Can I rearrange the sentence as Ein wichtiger Kurs beginnt morgen an der Universität? Does the meaning change?

Yes—the sentence is still correct. German word order is fairly flexible. If you start with the subject, you get subject-verb-time-place. The core meaning stays the same; however, the element you place first receives a slight emphasis.

Could I say Morgen ein wichtiger Kurs beginnt an der Universität?

No. Because of the V2 rule, the finite verb beginnt must be the second element. Placing the subject immediately after Morgen would push the verb to third position, which isn’t allowed in a main clause.

Is Universität always feminine, and how does that affect the article?

Yes, die Universität is always feminine. When indicating location you use an der Universität (dative). In other contexts, you might see zur Universität (movement: zu + der), but the gender of the noun never changes.