Staying outside the EU you require a residence permit to stay in the country longer than three months. Since the paperwork is essential and will be scrutinized you will do better using professionals to speed up the process or to avoid being rejected. Germany has several residences permits for various time periods.
Temporary Residence Permit
This permit allows you to stay in Germany for 12 months, but it can be extended too. Applicants need to state the reason for staying in Germany which is predominantly for studying or employment purposes.
The EU Blue Card
It is close to a temporary permit; however, the validity is longer. It is aimed at non-EU nationals that are highly skilled and has a job opportunity in Germany. These types of individuals typically have a masters or higher degree and you are more likely to get an EU Blue Card when having a Mathematics, engineering, technology or science background.
This card is valid for a four-year period after which they automatically get permanent residence providing they maintain jobs. Even though it is valid for four years it is possible to obtain permanent residency after 33 months. Individuals can get permanent residence when speaking or understand German after only 21 months when owning an EU Blue card.
With an EU Blue card, spouses can also live in Germany but only after obtaining permanent residence can the spouse apply for a job inside Germany.
Permanent Residence Permit
The permanent residence permit is also called a settlement permit and with this permit, you are not tied to living and working only in Germany. This permit entitles non-EU and individuals with an EU Blue card to become citizens after five years. German language proficiency is very stringent when applying for a permanent residence permit, and contributions and taxes must have been paid for five years. Spouses and dependents can live in Germany after an initial temporary residence permit that lasts a few years.
Since the paperwork is essential and will be scrutinized you will do better using professionals to speed up the process or to avoid being rejected. Germany has several residences permits for various time periods.