The German EU Blue Card is not an independent type of residence permit. It is a way for professionals to obtain German residency through a work visa...

Compared with the general work residence permit, the advantages of the blue card are mainly reflected in:

1) Pass the German Intermediate (B1) exam and apply for a green card after 21 months; pass the German Junior (A1) exam and apply for a green card after 33 months.
2) Approved, that is, a four-year residence permit is granted at one time.
3) You can apply for a residence permit for your spouse's family reunion at the same time. You can work immediately after entering Germany, either self-employed or employed. (General work residence permit, in principle, the spouse is not allowed to work in the first two years after entry.)
Compared with the general work residence permit, the high threshold for applying for the blue card is mainly reflected in:

1) Good educational background. It is better to graduate with a bachelor's degree in a better domestic university, and it is better to graduate with a master's degree or have a background in studying abroad.

2) The position in Germany must be remunerated with a gross annual income of at least EUR 55,200 (in 2020). A gross annual salary of at least EUR 43,056 (in 2020) is required for employees in the fields of mathematics, IT, natural sciences, engineering and human medicine. In such cases, the German Federal Employment Agency must approve your request for employment.  
In Germany, in addition to the employee’s monthly pre-tax salary, the employer also needs to pay about half of the employee’s insurance. Employees themselves bear personal income tax and half of the insurance. Germany's annual tax allowance is 8130 euros, using a gradual tax rate, the initial tax rate is 14%, the geometric cumulative tax rate applies in the middle, and the annual income of more than 250,000 euros, the maximum tax rate of 45% applies. Medical insurance: a total of 15,50%, of which employees bear 8,20% and employers bear 7,30%. Care insurance: a total of 2,05%, of which employees bear 1,025% and employers bear 1,025%. Pension insurance: a total of 18,90%, of which employees bear 9,45% and employers bear 9,45%. Unemployment insurance: 3% in total, of which employees bear 1.5% and employers bear 1.5%. In addition, employers also need to bear 0.15% of bankruptcy prevention funds. In other words, the employer must bear 19.425% of the pre-tax salary in addition to the employee's pre-tax salary.

Remarks: There is no immigration supervisor in Germany. During the period of residence permit, the applicant cannot leave Germany for more than half a year, that is to say, he needs to enter Germany once every six months. After getting an EU residence indefinitely (conditions similar to Germany's indefinite residence), you can enter the EU once a year. After receiving an indefinite stay, the residence permit will only be cancelled under extremely exceptional circumstances (such as a serious criminal offense).