Hello Valery,
I think its a Willow Warbler: good head pattern with long and broad supercilium and pale ear-coverts, strong bill with large pale base and the right wing structure. This is all in relation to Common Chiffchaff.
Such pale and greyish Willow Warblers are more common in eastern forms, and I think ssp acredula is common/the default form in NE_Turkey? I dont have personal experience with far eastern ssp yakutensis, but according to literature, only birds with a large pp and lacking any yellow tones to the breast can be identified with confidence. As your bird seems to have a normal/median pp and a yellowish wash to the breast, I think its better to call your bird a "Willow Warbler showing characteristics of ssp acredula".
Dark legs are said to be more common in this ssp