they have large greenhouses, the soil was damp, but it may have been watered after the sunstroke and yes the tree it's with me 4 days now . so you think it might be watering too little, because in my opinion the roots also seem ok. I thought the cold, but the plant comes from the valley where the temperatures are higher and a heat stroke in the greenhouse is probable
It's a Japanese white pine, they like cold.
Was it very warm there this summer?
I can't tell from the pictures, are there buds at the ends of the branches? Can you post a close up picture of them?
That will give us a better indication if the tree can survive, If the buds are in good shape, you have a chance, if they are dried out and dead, it probably isnt going to recover.
It's hard to try and determine what caused this, but I can give you advice based on what I know of the species.
I agree the roots look good, there is no root rot from what I can see from the pictures.
Put the tree outside but protect from wind and extreme cold. I wouldnt let it freeze at this point.
You removed the moss from the top of the pot so that is good, moss can make the soil stay wet for longer.
Be very careful about watering, use what we call the "chopstick method" to determine when it needs water.
The Chopstick Method: Place a wood chopstick or a piece of wood dowel into the soil and leave it there.
Take it out of the soil once a day and look at it. Water the tree when it is ALMOST dry, do not let it dry out completely.
Do this for at least a year.
Water needs change from season to season with the weather and growth patterns and this will teach you when your tree needs to water across those differences.
Watering is one of the hardest things to learn for newer people.
Beyond what I described above, just wait.
Do not give it fertilizer, Do not repot it, just wait, give it care and see if it recovers
Good luck