The International Office is unfortunately not in a position to influence visa processes in German embassies worldwide. It is not in contact with them and not familiar with the detailed visa processes of individual countries. Most likely you are applying with other students from countries with large intake numbers and it takes a long time for the embassies to process these applications.
It is possible for you to start attending classes as soon as you arrive here. That might be in the middle of term or even in the next term. This means you may miss classes and might have to defer a few exams to the next term. It would also lead to your study programme taking longer than you might have anticipated.
Please understand that it is up to you to decide, whether you are comfortable with arriving later and missing out on a few classes or even exams in the beginning.
Should you decide to come to THI, the International Welcome Center is looking forward to meeting you.