I personally don’t think it’s ever too early to start with a hangboard and here is the reason: The fingers are very slow to adapt. So starting off slowly, and building slowly, ideally over years is the best way to get strong fingers AND (most importantly) stay injury free. The best way to loose finger strength is to get injured…so start with the hangs early and progress slowly.
Here is an article that will help you get started
A few more tips:
If you’ve never done hangboarding before, then start easy! Way easier than you think. Easy enough that it doesn’t really feel like you’re doing much.
Be consistent. Start with 2x/week, this doesn’t sound like much but it is enough as the rest-spacing between is important for recovery).
Never climb and hangboard in the same day. After a few years, when you’re sending those 5.12s, then those tendons will be a lot stronger and that maybe okay.
Avoid pockets. They tend to be responsible for most injuries. So stick to edges and slopers for now.
There is tons of info on the web about fingerboards, not all of it is good and not all of it will apply to you. Do not ever imitate advanced climbers unless you yourself have become an advanced climber. That’s a sure way to get injured.
Hope this helps get you started. Good luck find the community there in Germany.