I am still inclined towards Cicadellidae. The head shape in Aphrophoridae is different. (Though Aphrophoridae and Cicadellidae are really closely related.)
"Rhytidodus decimusquartus, a member of Cicadellidae, Idiocerinae. I guess you collected it at light or in an evening room with open window. Lives on Populus nigra (including italica) and overwinters as adult. Zikade #1 is female, #2 is male.
Watch for Acericerus spp. in Gdansk, also in lit rooms during evening. None of the species is known so far north in Poland, but they all might occur. You can find a number of photographs in this forum.
Herbert Nickel"
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