I've found tickets with the help of agregator aviasales.
The trip was planned on the period of pandemia - January 2021. So many unexpected changes could happen with the flights (cancellations, airport closures, rule changes - how to enter the country and so on), all these have happend with our complex flight.
I've contact avia sales because I couldnt reach the tickets retailer directly (they had the restriction that they serve only customers, who have the flight in 2 weeks). I didnt expect that the agregator avia sales would involve in situation between me and tickets retailer. But they supported every my step and showed outstanding customer care! They contacted the retailer directly and pointed out on my situation, afterwards the conversation with the retailer started to be easier and nicer.
Thank to all Aviasales team!