Welcome pinewald -
The Italian Stone Pine is an outdoor evergreen and needs to be kept outside for the most part.
From what you say in your post it sounds as though it germinated early in the year in your house. It probably was OK by a bright window over the spring and summer, but as the light lessens and the house gets drier due to heating systems it needs to be put to sleep outside or in an unheated building or room.
It's needles are probably drying for the above reason. Even if you keep it alive until the weather improves (which is questionable) it will need to go dormant or it will wear itself out from lack of rest.
Ideally, if you have an unheated room, put it into that room and mist it, then move it to an unheated shed or garage by a window if possible so that it can go into full dormancy.
Pines need their rest.
"As the twig is bent, so the tree inclines"
"I rarely agree with most of what I say........." -
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