Is it possible for me to prepare for the German language test in time for the January intake?

It is unlikely you can reach the required German language level for the January intake if you are starting now. Achieving B1 proficiency usually takes at least 6 months of intensive study, and application deadlines for January programs are typically well before then.

If January is your target, consider applying to English-taught programs that accept English proficiency, and continue learning German for future options. Targeting a later intake would give you more time to prepare for German-taught courses.