Not a powerhouse. During the last years, the new Intel processors significantly improved in terms of performance but the Lenovo Yoga 520-14IKB still includes the older Kaby-Lake-processors. Read in this detailed review, why this low priced convertible will not get a recommendation in the end.
https://www.notebookcheck.net/Lenovo-Yoga-520-14IKB-i5-7200U-256-GB-SSD-Laptop-Review.267730.0.html