You may want to check G. tibetica, G.straminea or other related species from their group Leena.
Thank you Gabriela, you must be right that is is most likely G.tibetica. I googled them and it looks like that. If I understand correctly G.straminea flowers later than G.tibetica, and my plant grows in semishade so in sun it could flower even earlier. Anyway, I should move it to sunny position, because the flowers flop in shade.
Thanks for giving me a direction where to look, there are so many Gentians.