Thank you both Maurice and Ken.
Here the problem is sun light, we have very few in autumn and winter. I guess because we live just under some hills/low mountains, and when weather is not 100% clear here we have always clouds (infact when I move from my house down to the city I always find different light and temps). Autumn and winters there's poor sunlight.
The house is dark, too, I can't use windows interior sills because of the cats, so there's no good spot close to the windows.
In these days I see a good growth on DLs that are in the ground, most of them are growing new fans, I'm only talking about my seeds and my freshly sprouted seedlings.
I wanted them to grow as big as I could before next spring but maybe it's simply not possible due to environmental conditions.
I guess I will bring them back inside until they are grown a bit, then put them in bigger pots and put them again outside, since bigger pots won't fit anywhere inside (should I prefer deep pots or large pots for roots?)
Do I have to prefer warmth or light?
As a side note, do any of you know if DLs are toxic for cats? Many plants are, but I can't find any information here since they are rarely grown.
Many thanks!