Translation:I do not have time because I am working.
You're right, but we've got a ridiculous amount of words for conjunctions too:
- because, as, since, due to
- thus, therefore, consequently, as a result, so
- but, although, however, whereas, nevertheless, nonetheless
- and, in addition, also, as well, what's more, moreover, furthermore
And these are just grouped into four approximate types, there are many more. At least these ones we're learning now don't (so far) take different grammatical forms as ours tend to. :)
What is the rule with commas? Is it that there's (nearly) always one before a conjunction?
Mostly... generally, if it introduces another clause, there should be a comma. I myself am not great with those, and sometimes we just need to check on the Internet.