Hi Matus,
Whenever i've had problems importing an OAS/Swagger it's been due to one of two reasons, either:
I was trying to import an OAS/Swagger of version not supported by ReadyAPI!'s import tool
OR
The OAS/Swagger contained errors.
ReadyAPI used to support swagger v1.0 and v2.0 and OAS v3.0. I think OAS v3.0.3 is the latest OAS, but looking at your error detail i think you have 3 errors in there....attribute topics and attribute areas are unexpected and your attraibute paths is missing.
Have you opened your yaml in https://swagger.io ?
I'd suggest having a look in there....swagger.io is pretty good at identifying errors so you can fix them.
Cheers,
Rich