zaczęli

third-person plural virile past of zacząć

biec

1. to run (of living things: to move quickly on foot)
2. to run, to rush (to rush somewhere in order to accomplish a specific task)
3. to run, to race, to roll (to move across a surface in a particular direction)
4. to run, to go, to lead (to form a route)
5. to fly, to race (to pass by very quickly; to proceed very fast)
6. to progress (to develop or change with time)
7. to begin, to run (to begin and continue)

gdy

1. when, as
2. if
3. whereas
4. when; Further details are uncertain.

pierwsze

1. inflection of pierwszy:
2. inflection of pierwszy:

krople

nominative/accusative/vocative plural of kropla