Is будь ласка now standard for the word "please", or has прошу dropped out of use in Ukraine? I remember my grandparents would commonly use прошу to say please.
Будь ласка - please or you're welcome, прошу - you're welcome
Also use прошу when you want someone to repeat what they said, because you didn't understood it. Quite handy phrase when you are a beginner :)