Combining multiple verbs


I work in a hotel and I was asking a coworker if we are permitted to drink the
coffee in a certain location near the desk. I am trying to be formal with this
request.

I asked "Are we allowed to take that coffee?"

In romanji "Sore Koohii o teru kyoka sa retamasu ka"

1) Am I allowed to combine verbs like this? Under what circumstance can I do
this?

2) In order to be polite is it ok to add the masu to the last verb or do I
have to add it to Teru as well?

3) How would I make this sentence casual?

