This is the 3113th most frequent Polish word.
prosto
"Prosto" means "straight" or "simply" in English, depending on context.
Here, 'prosto' functions as an adverb describing the direction of movement—straight ahead.
Idź prosto przed siebie.
Walk straight ahead.
Here, 'prosto' means 'simply' or 'in a straightforward manner,' indicating clarity and directness in speech.
Powiedz to prosto, bez użycia trudnych słów.
Say it simply, without using complex words.
In this case, 'prosto' means 'straight' metaphorically, signifying sincerity coming directly from the heart.