Breakdown of Почему вы опровергаете эту достоверную информацию?
вы
you (plural)
этот
this [f: эта, n: это]
почему
why
информация
information
Questions & Answers about Почему вы опровергаете эту достоверную информацию?
How could I add якобы to this sentence to show I don't believe the information is actually reliable?
Could I use мол instead of якобы here to mean 'allegedly'?
Not quite. While both express doubt, мол is used to quote or paraphrase what someone else said (like 'they say that...'). Since you are describing the noun информацию as allegedly reliable rather than quoting a statement, якобы is the right choice. If you used мол, you would need to structure it as a reported claim: Почему вы опровергаете эту информацию, она, мол, достоверная? (Why are you refuting this info, which they say is reliable?).
Both достоверный and надёжный translate to 'reliable'. Could I use надёжную here instead?
No, they are used differently. Достоверный applies to facts, data, or information, meaning 'authentic' or 'credible' (literally 'worthy of trust'). Надёжный is used for things or people you can rely on to perform well, like a reliable car (надёжная машина) or a reliable friend (надёжный друг). For a 'reliable source' of information, you would use надёжный источник, but for the information itself, it must be достоверная.