This is how the Lemonia square looked today:
In my opinion, what matters most is to prevent such activities from happening again and educate people to respect their urban enviroment, which is an important factor for our culture.
What is left now...
What could be done to prevent actions like this in the future? One proposal is to protect the trees by encircle them with special metal latticework, called "tree guards" which will protect them efficiently from damage. This practice is quite common in several countries in Europe. (Tree guards in Sweden).
Two renders of how it could be done in our case, made by a friend: