Why is the duration of the stay visa to Germany 90 days?

Well, I'll give you a short-term visa for three months first. When you arrive in Germany, remember to do a good job in banking, insurance, household registration, housing contract and admission certificate, and then take these to the local immigration office to apply for a long-term visa. Generally speaking, if the materials are complete and meet the application conditions, you will be granted a long-term visa of 1 to 2 years.