Learn Turkish: Yoksa burada bir terslik var da biz mi aldanıyoruz? - Is there a problem here, and are we being fooled?

While yoksa does mean "or else" in conditional sentences, here it acts as a marker of suspicion or sudden realization. When placed at the start of a question, it translates to something like "Could it be that...?" or "Don't tell me...?" It shows the speaker just had a worrying thought that they are now vocalizing.

Why is the question particle mi placed after biz instead of at the end of the sentence (aldanıyor muyuz)?

In Turkish, placing the question particle directly after a specific word puts the interrogative emphasis on that word. By saying biz mi aldanıyoruz, the speaker is emphasizing "we" — asking "Are we the ones being fooled?" If it were at the end, it would just be a neutral question about the action itself.

What is the role of the particle da right after var?

The particle da here acts as a conjunction connecting the two clauses: "there is a problem" and "we are being fooled." It translates as "and" or "and so" in this context, building a logical bridge that implies one clause might be the consequence of the other.

The word for "problem" here is terslik. How is this word formed?

It is built from the adjective ters, which means "reverse," "backward," or "opposite." By adding the noun-forming suffix -lik, it becomes terslik, literally meaning "wrongness" or "contrariness." It is an extremely common way to say there is a "hitch" or "problem" with a situation.