fine-tune (one's) skills

Translations
оттачивать (чьи-то) навыки
He is taking extra classes to fine-tune his skills.
Он посещает дополнительные занятия, чтобы оттачивать свои навыки.
Definitions
To make small adjustments or improvements to one's abilities or expertise in a particular area through practice, training, or experience.