call in sick 请病假

take the day/week/month off

come down with the flu

I was hoping to take the day off

To describe sick

a headache; a running nose; slightly feverish

A sore throat, a sore back, a sore neck

Quite ill = sick

slight feverish 

Check in the hotel/restaurant~    have a reservation under the name (of)

overbooked: a hotel/restaurant  is more than full

complimentary upgrade: free improvement of quality

concierge: hotel employee that helps guests

deluxe room: hotel room, better than standard

mix up =~ confusion / misunderstanding

The timing is just not right

to take some of the weight off my shoulders

keep our costs down =  do not have the unnecessary spending 

too risky to take on new staff

understaffed = short staffed

cut cost: reduce spending

elaborate on sth.