think (about), have an opinion (about)
Si opinas sobre su trabajo, ten en cuenta también su falta de experiencia.
If you're going to give your opinion on their work, also take into account their lack of experience.
Es tan importante amar a alguien para casarse ¿Qué opinas?
Is it really important to love someone in order to get married? What do you think?
— Do You Thing (2001)
Entonces, ¿qué opinas de ella?
So, what do you think of her?
No sabes nada sobre el tema y opinas como si fueras experto.
You know nothing about the subject and you give your opinion as if you were an expert.