This is the 3135th most frequent Portuguese word.
certas
"Certas" means "certain" or "some" in English.
Here 'certas' is utilized as an adjective meaning 'correct' or 'right,' modifying 'opiniões' (opinions).
Algumas pessoas têm opiniões certas sobre o assunto.
Some people have correct opinions about the subject.
In this context, 'certas' acts as an adjective meaning 'certain' or 'specific,' providing a generalization or vagueness about the noun 'dificuldades' (difficulties).
Certas dificuldades podem surgir ao longo do caminho.
Certain difficulties may arise along the way.
Similarly, 'certas' here serves as an adjective translating to 'certain,' indicating particular times within a general timeframe, modifying 'horas' (hours).