Hi @bit0rain, thanks for getting in touch.
To start developing interaction applications with the Tobii Eye Tracker 5 you can a couple of options:
1) The Tobii Interaction API which is the recommended route for getting up and running quickly
https://developer.tobii.com/product-integration/interaction-library/
2) The Tobii Stream Engine API which is a low-level SDK catered for more advanced users
Please check these out and let us know how you get on. Best Wishes.