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My 1930s house was laid with hydro-gypsum board and Pregystyrene slabs with glue pads, leaving a 1cm air gap; now, the walls are not very healthy (machefer); is there a risk of moisture? moreover all the windows and doors have been changed over time, but none has a ventilation system; so the air does not circulate. what to do? apart from creating drafts by opening the windows?

Glue drywall on a wall of cinder blocks does not pose a problem if the wall is not wet (the reasoning also applies to other materials such as brick, traditional stone block, stone, etc.) If moisture problems occur, the causes may be multiple: porosity of the facade plaster, capillary lifts from the ground, cold wall phenomena, condensation, etc.
This last case is quite common when old windows are replaced by new, sealed ones. Without VMC, the risk of condensation is real, but again, many old houses without VMC and equipped with new windows behave very well, each case is special.
If in this configuration your house stays healthy, do not do anything.
Your final remark, open the windows, is common sense, including in winter, but sometimes we forgot this simple action.

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