Hi @Carlos-and-Anita0,
that's too bad for you, I am so sorry. I know a few cases, where Airbnb recently was quite supportive and even completely removed the guest's acount due to a serious damage.
Eventually your case just has been mucked up from the beginning. Next time you need to open a case with airbnb before the guest does it, but next time probably will be totally different.
One question about the penalties: did they just block this one appertment? or also the other ones (I have seen you have 3 apartments in total, right? and is it a long period, which has been blocked is blocked?
To avoid cases like this, you may need to rework your house rules to clearly define what the guest need to do and what is forbidden, also you can define what has to be done in case of this or another problem.
Fortunately I never had a problem like this, even if I had more than 200 guests from all over the world. Hopefully you are not giving up due to this unlucky case and will continue to host in the future.
I wish you all the best and a lot of just normal & friendly guests!