EU citizens and citizens of Norway, Iceland, Liechtenstein and Switzerland (EFTA states) have a right of free movement for Germany. Therefore, you do not need an application or permit for entry and residence.
In principle, you can prove your right to freedom of movement with your national passport from your country of origin or your identity card. Since 2013, proof of the right to freedom of movement is no longer issued. An application or a visit to the Migration Office Bremen is therefore no longer necessary, but also no longer possible.
However, if you not only want to visit Germany/Bremen but also want to live here, you must work, study or complete a training course in Bremen or you must be a relative of someone who is entitled to freedom of movement.
In this case it is sufficient for your legal residence that you register your residence at the Citizens' Office.
Family members of EU or EFTA citizens who are not themselves nationals of these countries require a residence card if they wish to live in Germany/Bremen.
As soon as you have been working, studying or training in Germany/Bremen for five years, you and your relatives can apply for a permanent residence certificate or permanent residence card at the Migration Office. This does not apply to Swiss nationals. You can apply for a settlement permit.