Image Processing People Counter Through Doors

I want to install ip cameras at the exits of the locker rooms in the gym where I work. Within the scope of pandemic measures, I want to know the maximum number of people inside and warn people with the help of a screen when the maximum number is reached. I have some experience with software. So far I can count people on windows with python and send them to webserver with the help of flask. I can also pull the information on this webserver and show the maximum number on the raspberyy pi screens at the entrance of the doors. The first thing I ask for your help is I can't count people with high accuracy because of shadows. The second issue is that when I want to process more than one camera image with the help of threads, both the computer does a lot of processing and the results work with less accuracy. IP cameras and raspberries were installed. There are 3 different dressing rooms and 2 doors in each room, a total of 6 ip cameras and 6 screens. Since the algorithm has 2 cameras on each door, each screen will add up and display its own camera and the total number of people of the camera on the other door.