Your best options for pecans are Campbell NC4 (type 1), Warren 346 (type 1), and Lucas (type 2). Pecan needs both type 1 and type 2 planted nearby to pollinate each other. You may also be able to grow Hark (type 1) and Kanza (type 2) but I suspect summer heat units will not be quite enough for them. Your climate is roughly similar to parts of Wisconsin in the U.S. Qroksy is in Croatia and sometimes posts here. He has a fairly large number of pecan seedlings including quite a few from Kanza.
Here is a link to a thread on pecans that includes a few sources in Europe. See post 151 by Barkslip.