I am not very sure but could be some species of Ulmus.

And what about Celtis it is more probable than Ulmus.

Not certain, but it does look like a lot like a Celtis

Dear all, 

It seems like certain species of Euonymus or Ulmus, due to the suberin cork. As far as I can notice, the leaf is not asymmetrical? If not, my guess is more likely to be Euonymus (though the cork is more similar to Ulmus).

Best regards! 

 It is Ulmus

It seems like Ulmus minor (campestris), but i'm not sure !

Ulmus parvifolia

Thank you all for your help!

I agree with Dr. Libor Ekrt and Dr. Patrick J. Mcintyre - Celtis it is more probable than Ulmus.

Celtis sp.  Similar to Celtis occidentalis L. or a related eurasian species.

It seems like to Celtis.

Ulmus usually have uneven leaf bases. The pictured leaves don't.

Thank you for your attention to this matter. It was very helpful!

 i also suggest a specie of "Ulmaceae" family.

Thank you for your answer!

It could be Celtis, perhaps Celtis caucasica?? (now belonging to Cannabaceae, formerly Ulmaceae).