Hey, have a great February day, everybody, this is my first tree picked up in the wild, I took it in the forest undergrowth.
The question is can this tree be called a yamadori?
I would estimate the age to be around 50 years old.
I haven't done anything to the branches yet.

Yea! All tress you get from the wild and dig up are yamadori, to me the tree looks 20-30 years old.

I think i read here on the forum that not every tree collected in nature can be called ,,yamadori"

This hobby is so full of nomentaclures, rules and classificatins. In the end you decide what you want to call your tree. You also decide what you want it to be in the future. And that is far more important than what you call your tree.

In the strict meaning of the word yamadori it means tree from the mountains. So purists can say that if it is not from the Mountain it is not a yamadori. So they come up with alternate names for trees collected elswhere. All of them a mix of english and the original word. Bogadory, urbandory, gardadory and a lot of other strange names. I bet the japanese people laughts at us.

So just focus on r the future for your tree and stop worrying about naming conventions, because there are none.

Regarding the age. I collected a bog pine upnorth Sweden for a literati project. It had about 2 cm thick trunk. Unfortunattely it died. So I got a chanse to get a part of the lower trunk to count yearly growth. I had to use microscope. It was more than 100 years old, proboably 120, just so hard to count.

It is not possible to tell the age of a living tree without killing it. Yes, there are the carbon 14 method, but that is not awailable to hobbyists.

But again. It is not important. In bonsai we strive to create an image of an old mature full scale tree. Image is the key word. If you success in making a 20 year old tree look like 100, you are successful. If you collect a 100 year old tree, but fails to make it look like an old mature miniature, you better go for option 1.

How long should the tree remain in the training container without transplanting and pruning?
I calculated that this year 2024 will remain without intervention, next year 2025 I would reduce the depth of the container (now it is 40cm because of the roots that the tree has grown), replace part of the soil and make the first cut and wire, and then see how the tree will grow

Tha answer is as usual "it depends". I would not make up a plan for 2025 before I know how growing season 2024 went. Most of my colected trees are in training pots 4-5 years before I even think about shallow pot. There are no reason to hurry.