I found a bunch of these up on one of the mountains outside town and brought a few back. They're a little wilted now because I took a while to properly replant them, and I haven't removed the dead leaves at the bottom yet, but they seem pretty hardy!
It is difficult to see from this picture. The genus should be Sedum, which is very frequent in Europe.
It is a succulent plant, so various species are adapted on very hot climate, but some also on very cold climate, which is also dry (as not as "lack of water, but lack of "liquid water" and dry air).
Give it sun, and cover with some more soil, so that it can form new roots.
The segments are still "fat", so you do no need to water now (risk of rot). Wait few weeks, so that the plant will build new roots.
For final identification, we need to see the flowers. They are often white or yellows (some also red). Some species have larger flower. It is a nice plant for stone garden.
PS: I'm not sure you used the right soil. You should check if Thessaloniki soil is limestone.