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Hi Karol,
definitly Chalcidoidea, but I'm not sure with the family. It might be a Pteromalidae, but the chalcidoid wasps aren't easy for ID.
Further pics with details on the antennae, the head and the legs could help to go further.
(There's a paper called "Keys to the Chalcidoidea fo Czechoslovakia from Peck, Boucek and Hoffer, published 1964 in the Memoirs of the Entomological Society of Canada, No. 34 - but without deeper knowledge of the chalcids, more pics on the mentioned details or the specimen itself you might get lost...)

Maybe you can try at Hymis.de, there are some specialists.

Best regards,

Marc