Hi and welcome 
Sorry to hear about the park. Perhaps there is inspiration to be drawn from members of the community who are facing the same struggles. So some people who immediatey come to mind are:
@jordan : https://edgeryders.eu/en/the-urban-shepherd-of-stockholm
@Nick_Davitashvili: https://edgeryders.eu/en/better-and-bigger-collective-action
This work of building and caring for communities is challenging.
As @marcoclausen points out
@marcoclausen, @ecl and @Caroline have alot of experiences in Berlin: See their stories here. But this kind