The property has hung the banner in front of my window. Can I take it down? Completely blocked the light on my windowsill! They must bear the responsibility of hanging banners without our permission.

Whether to bear legal responsibility depends on whether they have obtained legal procedures, such as whether they have been approved by the urban management and so on. As owners, they have the right to ask the property to remove or move the banner to other locations or directly complain to the local urban management department, and try not to take it down by themselves. My suggestion is to negotiate with the property first, and complain directly to the local urban management department after the negotiation fails, which is reasonable, legal and well-founded.