Welcome to permies Sonce
I imagine it gets pretty dry in Macedonia?
I'd use sawdust as mulch if I didn't have something else around, and I wouldn't worry about acidity.
But I'd be wary of using an unmixed layer or it could get a real water-repellent crust.
Do you have any
trees dropping their leaves ? I'd mix the sawdust with leaves, grass, seaweed, weeds, very fine twigs etc, to make a porous and non-compacting mulch.
On a side note, unless you're using cardboard specifically to kill difficult grass or something, and especially if your climate is dry, I'd leave out the cardboard layer if you have
enough goodies to bury the grass etc.
If it dries out, cardboard can take
forever to break down!