This is the 2861st most frequent Polish word.
kupując
"Buying" or "while buying."
Here, 'kupując' functions as a gerund in a participle clause, indicating an action related to the main verb (choosing).
Kupując kwiaty, zawsze wybieram róże.
When buying flowers, I always choose roses.
In this context, 'kupując' describes the manner or reason of the main activity (studying).
Uczyłem się matematyki, kupując nowy kalkulator.
I was studying math by buying a new calculator.
'Kupując' introduces a simultaneous occurrence or circumstance during an event described by the main clause (meeting a friend).