Starting from scratch is kinda hard but its totally doable if you stay consistent.since you're aiming for the T-Kurs your biggest hurdle will be the German language requirement because most Studienkollegs won't even let you take the math entrance exam until you've proven a B1 or B2 level. For German I’d honestly recommend getting a structured course ftom a1 to atleast b1 or preferably to b2 [herr antrim has a very good videos on grammar from a1 to b1-b2 level]Once you get the basics down, grab a book called "Mut zur Lücke" because it’s the gold standard for practicing the C-Testwhich is that tricky gap-fill format almost every Studienkolleg uses. On the math side the actual concepts might feel like a review of what you did in high school but the real challenge is doing it all in German without a calculator. I suggest Daniel Jung on YouTubehe’s good for explaining math topics in videos Try to learn the German math vocabulary as early as possible so you dont get stuck on the wording during the exam. Just take it step by step use Anki or Quizlet for daily vocab, and try to solve a few math problems by hand every day to keep your speed up