GRE

Yes, GRE is still required as dMAT has not replaced it. dMAT is an aptitude test required for the APS documentation process, and GRE is a university admissions test. Both these exams differ in their purpose and the courses/documents they're used for.
On a completely different note, you may check with your German university whether they can waive the GRE requirement for your case or not. It's completely the university's call.  

A GRE score is recommended (not mandatory) for admission to MS in CS course of Michigan State University. For the recent admitted class of MS in CS of MSU, the following were the stats of the students-

• Quantitative: 164
• Verbal: 153
• Analytical Writing: 3.0

A GRE score is recommended (not mandatory) for admission to MS in CS course of Michigan State University. For the recent admitted class of MS in CS of MSU, the following were the stats of the students-

• Quantitative: 164
• Verbal: 153
• Analytical Writing: 3.0

GMAT/GRE scores are not a compulsion for MBA courses at Dublin City University. Though they can be added to strengthen the application along with the updated Resume, Bachelor Degree, work experience, English language tests, statement of purpose and recommendation letter.

Beginners should focus heavily on high-weight math topics like Number Systems, Averages, Percentages, and Ratios.

These core concepts appear much more frequently. Practicing on questions related to these topics will help you.

Beginners need 2 to 3 months for GRE preparation. You should have a proper study plan, regular practice, and consistent revision.

The exam is new for you, but the core syllabus is not new for you. All you need to brush up on your learning is well.