Understand I dag jobber jeg and how an opening adverbial changes the subject’s position.
Second constituent, not second word
In a declarative main clause, the finite verb takes the second constituent position. The first constituent may contain several words, so counting individual words gives the wrong result.
Hver mandag morgen tar jeg bussen til jobb.
Hver mandag morgen is one time constituent, followed by tar and jeg.
Change the opening, keep the meaning
You can begin with the subject, time or place to change emphasis. When an adverbial opens the main clause, the subject normally follows the finite verb. Do not add an auxiliary just to satisfy V2.
Jeg bor i Oslo. I Oslo bor jeg sammen med familien min.
Notice bor jeg after the place expression.
The finite auxiliary comes first
With a verb phrase, V2 applies to the finite auxiliary such as har or skal, not the participle or infinitive. The other verb remains later in the clause.
I morgen skal vi besøke vennene våre.
Skal is finite; besøke is the later infinitive.
Try it yourself
Rewrite Jeg leser norsk på biblioteket starting with the place, then with I dag. Check the position of leser both times.