Please help with the text

Based on our observation yesterday evening, there were still significant number of drinking and food cans found accumulated at our assembly hall after your activity. In accordance with our pre-activity mutual agreement, you have to remove all your leftover before handing back the facility to us. Obviously, you have seriously violated the regulations and if we don't see any clearance action taken by you by next week, it will assume that you decide to surrender the deposit of $800 for the holding of activity to us.