Oleksii said:
... next week weather will be great to plant, I'll buy 2 package of soil for plants (20 liters reach) to add when planting and also cover at the top to protect for some time from night cold.
Don't add anything but the native soil to the planting hole. Adding other better soils slows the transition of the roots into their new environment. The roots will expand into the native soil much faster without your well intentioned intervention. What will help is loosening the soil so the roots have any easier time.
Don't add anything to the top of the root ball as that will cause crown rot. Plant the tree just a wee bit higher than it was in the pot so when the soil settles, the top of the roots will be at ground level.
