Holders of this sort of long-term D-Visa are issued with a different residence title (residence permit, EU Blue Card) six weeks before the visa expires at the earliest.
Is your stay not expected to be longer than the period for which the visa is valid?
Then an application does not have to be made. An interview at the Berlin Immigration Office (Landesamt für Einwanderung) is also unnecessary.
Is your stay expected to be longer than the period for which the visa is valid?
Then apply within the validity period of your visa for the residence title to be issued. This application should be made four to six weeks before the expiry of the visa.
Working with the national visa?
It says in your visa whether and to what extent you are permitted to work.
You can begin to work to the permitted extent immediately after entry, even if you still do not have a residence permit or an EU Blue Card.
Holders of a one-year visa for study purposes are permitted to work in accordance with Section 16b paragraph 3 AufenthG. This means that, with this visa, you are permitted to work a maximum of 120 whole days or 240 half days per year as well as to undertake part-time student work.