Questions & Answers about Θέλεις να κάνουμε μια βουτιά πριν φάμε;
Θέλεις means you want or, in a question like this, do you want? It is the 2nd person singular form of θέλω (to want).
So it is addressed to one person, informally, like saying Do you want...? to a friend, partner, sibling, and so on.
Να is a very common Greek particle used before a verb in clauses like:
- I want to...
- Can I...
- Let's...
- It is necessary to...
In this sentence, θέλεις να κάνουμε... means something like do you want us to do... or do you want to... with the idea of a following action.
English often uses to here, but να is not exactly the same as English to in every situation. It is just the normal Greek way to introduce this kind of verb clause.