Booleans doesn't work with the engine..?

[vdud]

I am trying to add Booleans as a window cutout. but it's taking all the Booleans at once. I know I'm doing something wrong here. but couldn't figure out, tried 3 ways to generate. here are the screenshots of those. and still get the same result. I believe their location needs to be changed at every generation.

Final result every time:

[cjwmaya]

你好，我是也毛儿，信件已经收到，