Learn Danish: At vildsvinet kommer løbende på marken, overrasker jægeren. - That the wild boar comes running in the field surprises the hunter.

The entire clause At vildsvinet kommer løbende på marken acts as the subject of the sentence. Because it occupies the first position, the main verb overrasker must immediately follow it to satisfy the V2 (verb-second) rule. Notice that because the fronted clause is the subject itself, we don't invert a separate subject and verb afterward; it simply follows a Subject-Verb-Object pattern.

How else could I structure this sentence if I do not want to topicalize the at-clause?

You can use the dummy pronoun det (it) as the formal subject and move the at-clause to the end. The sentence becomes: Det overrasker jægeren, at vildsvinet kommer løbende på marken. Putting the clause at the front instead (topicalizing it) places heavy emphasis on the surprising event itself.

Why is the word løbende used here instead of a normal present tense verb like løber?

The phrase kommer løbende uses the present participle (the -ende ending) alongside the verb at komme (to come). Danish frequently pairs at komme with a present participle to describe the continuous manner of motion, translating directly to "comes running". You cannot use two present tense verbs like kommer og løber to express this specific continuous meaning.

We say "in the field" in English. Why does the Danish sentence use på marken?