These are coordinating conjunctions, see the tips for Conj. 1. Lesson:
Relevant section: The common Dutch coordinating conjunctions are: en, of, maar, want and dus.
There are only five of them, so learn these by heart! In comparison, there are many different subordinating conjunctions. Those bring along complicated rules for word order in subordinate clauses and are treated in a later skill.
So if you are using these 5 coordinating conjunctions, word order does not change: en, of, maar, want and dus.
This is tricky. In American English, at least, we would more likely say "We are going swimming." But this is not in the future tense. It is the present continuous that indicates a future action, like "We are having a big party next week."
Strictly speaking, "We are going to swim," is future tense. So for the purposes of this translation, it's more accurate.
And try this on for size: "Because it is warm, we are going to go swimming." It would not be unusual to hear that around these parts (except it would sound like "... we are gonna go swimming"). That is because "to go swimming" is a set verb phrase that means, basically, to engage in the act of swimming. We also do this with other activities, like dancing, fishing, etc. In our minds, then, "go swimming" feels like a single verb, so it seems perfectly natural to use "going to go swimming" for the future tense.
I don't think there's any problem with that grammatically, but it's not how a native English speaker would phrase it. I think the problem is that "go to" is usually followed by a place, so it looks odd when followed by a verb. With verbs we usually use "go <gerund>" or "go and <infinitive>" instead, or sometimes "go to <place> to <infinitive>" (if we want to explain why we're going to the place).
The English "we are going swimming" does imply a future tense, even though it doesn't look that way grammatically. You wouldn't say it if you were actually swimming now. You might be on your way to swim, or you could be referring to some time in the future - for example, you could say "we are going swimming tomorrow."
"We're going to swim" and "we will swim" should be fine, but they seem a bit less natural to me.