Dell Optimizer app does not disable proximity sensor

After 40 seconds my laptop screen goes black and when I move the mouse or touch the keyboard, I have to login again. All inactive settings in Windows are set to a longer duration so I found out that this is caused by the Dell Proximity Sensor. I opened the Dell Optimzer app and disabled the Proximity Sensor but my laptop is still shutting down when there is no activity for 40 seconds.

I like the proximiy sensor and would prefer to start it after 5 minutes or so but also when I set a longer duration, it still starts after 40 seconds. This is very frustrating.

Thank you for your help