Desktop Screen Switches when I open 2nd Application -How to Turn this feature OFF

I have gone to system preferences-> mission control-> all boxes unchecked, but still have the issue.

I know this is SUPPOSED to help you keep organized but I find it VERY annoying. Many times I need both applications open in order to complete a task & this 2nd desktop is no different that opening one window, closing it, opening another, writing down what I need, lowering that window, opening first window to record some info, then repeating until task is done. It is a useless feature that just takes up memory space. I would never use this feature. Only good if you are at work, doing personal tasks & being able to switch back to other desktop if boss comes around. I have search on the internet & most advice seems to be from 2012 & their suggestions have not worked with Mojave (nope, won't update until I am sure bugs worked out).:-) PLEASE someone advise me as to how to disable this feature, anyone?