Problem: either a disease or spoiled soil. How to tidy up fruit trees?

Dear Colleagues! I got a plot in Bulgaria where no one had done anything for about ten years. There are fruit trees.

The common problem is no harvest. The fruits are small.

Symptoms:

There are many weak, almost withered branches.

The leaves on all the trees appear to have dried out areas.

There is lichen on the trunks.

Now about each:

Quince: When I arrived there (at the beginning of summer), there were wrinkled brown fruits hanging on the tree. I decided that last year they were not collected - they dried up. However, new fruits appeared and developed, quite large, some slightly deformed. In early September I left, and when I returned a month later I saw that my quince fruits already had the same appearance as last year’s: again dried out, wrinkled and darkened. The neighbors had large ripe pears and grapes hanging.

Cherry: There are quite a lot of berries (although they could be larger). Sometimes there were worms in the berries. In mid-August it suddenly began to shed its leaves, and by September it was almost bare. At the same time, the neighbor's cherries remained in the foliage.

Plum: There are many “daughters” around and nearby, apparently because no one collected the fruits. Almost overgrown. There are quite large fruits (about 25 mm), but mostly they are small, the size of a good cherry. All signs show that the fruits are of the same variety, even on the same tree as large ones. Plus general symptoms.

Apricot: The tree is about four meters high, and only has two fruits.Normal, large, tasty, but only two. And there is very little foliage.

Walnut: A large tree, about eight meters high, spreading... Walnuts are very modest in size, and frankly speaking, they are not dense for such a large tree. There is a hollow in the trunk. Some bird lived there. On the road in the village there are nuts growing - at least twice as large, and there are a lot of them on the tree, but I can’t see them, there are so few of them. And by the way, the nuts fall green. I was told that they must ripen on the tree.

A huge colony of ants was discovered on the site. We offended them a little and they left.

I intuitively guess that I need to get rid of the withered branches and “daughters”, feed them properly, and treat them for some disease. The Bulgarian neighbors say that this disease also happens on grapes, it’s called either a dry leaf or a burnt leaf... Also, a neighbor said that in the spring there was some kind of acid rain, and that all their tomato tops turned brown. Then the son came, treated it with something, and saved it. I asked the Bulgarians everything I could. Specifically, I didn’t learn anything practically useful. There is nothing to water against infection, nothing to protect against this acidic... Either they don’t understand me, or they really don’t know anything anymore, or they have their own national characteristics....

Another interesting fact: Carrots, radishes, squash, dill, and cilantro were sown. So: The carrots grew as big as a finger, the radishes - literally a few of them grew to about 40 mm in diameter. The rest are 20 mm, like peas! Dill in general is a small herb and sparse. Patissons - nothing like that. Normal.

Maybe the reason for all the troubles is that the soil is saturated with these acids? By the way, stores sell a soil analysis kit. I think it’s not in vain. There is demand.

I would be grateful for tips from experienced gardeners and farmers: Firstly, is it worth pruning healthy branches so that the tree develops not in favor of thin branches, but in favor of the trunk and powerful branches.

By the way, I’m thinking of transplanting some of these “daughters”. Tell me when is the best time to do this.

Thirdly, how to treat this disease and if the soil is saturated with this acid rain, maybe it makes sense to treat it somehow?

Fourthly, what and how to feed?

When should all these procedures be carried out?

Thank you very much for your attention to my rather long question. Perhaps, in the opinion of the forum administration, the topic is posted in the wrong place. I apologize and ask that you move it to a better location.