dessas

In a sentence

• Eu gostaria de provar uma dessas sobremesas.

  I would like to try one of those desserts.

  Here, 'dessas' is used as a demonstrative pronoun, referring to specific desserts known to both the speaker and listener.

• Ela evitou cometer erros como um desses.

  She avoided making mistakes like one of those.

  Here, 'dessas' implies belonging to a certain category the speaker is discussing.

• Você já viu histórias como dessas em algum lugar?

  Have you ever seen stories like those somewhere?

  Here, 'dessas' refers to specific stories of a certain kind or context previous discussed.