Sometimes translators have to make a decision; sometimes there is no ambiguous option. In 2 Cor 4:6, is the gospel glorious or is the gospel about the glory of Christ? It is one or the other, not both.
Why do translations all say that Jesus gave up “his” spirit when the Greek behind “his” is the definite article, “the”? This is a good example of why knowing a little Greek may not always be helpful and why I wrote Greek for the Rest of Us.
Paul uses a grammatical device called “epexegetical” to explain what the “mystery” is. There are several ways of doing this, but in Ephesians 3:6 he uses an epexegetical infinitive to show that Jews and Gentiles alike are fellow heirs.
We teach students to translate ἐάν as if, but often in a third-class conditional sentence doing so misleads. Sometimes "if" brings in an element of conditionality that was never intended by the speaker/writer."