My co-workers don’t pull their weight, and I’m always picking up the slack.“
The idiom “pull your weight” means to do your fair portion of the work or responsibility. So if your co-workers aren’t pulling their weight, it means they are being lazy and not contributing as much as they should.
As a result, you are always “picking up the slack.” This idiom means to do extra work because other people are not doing their part.
#2 – “I can’t stand the office politics. It seems like kissing up to the people who call the shots is the only way to move up the ranks.”
The expression “office politics” refers to people using their power/influence in a company to get advantages for themselves. It’s usually a negative thing.
The phrasal verb “kissing up to someone” means to say and do lots of nice things for a person because you want to get on their “good side,” so that they will favor you or help you. Another way to say this is “buttering someone up.”
The people who “call the shots” are the people who make all the important decisions.
The idiom “move up the ranks” means to get a higher/better position in a hierarchy. In the context of a job, this would mean getting a promotion, a better salary, or more authority in the company. Another idiom for this is “move up the totem pole.”
#3 – “My boss loves to micromanage and I can’t do my best work when she’s constantly breathing down my neck.”
To “micromanage” is to try to control every single detail of a project or of someone’s work.
The idiom “breathing down my neck” means the boss is closely watching or monitoring you. Imagine a person standing behind you, so close that you can feel his / her breath on your neck. This is considered very annoying!
#4 – “The job itself is rewarding, but the salary and benefits leave a lot to be desired.”
The word rewarding means something that gives you satisfaction and makes you feel good. You can describe a job, volunteer work, or helping other people as “rewarding.”
The idiom “leave a lot to be desired” is a polite/indirect way to say that it is unsatisfactory, it is not as good as you would like it to be.
#5 – “I feel like I’m spread too thin, but every time I wrap up one project, I’m given two more – which, of course, need to be done yesterday.”
The idiom “spread too thin” means that you are trying to do too many things, projects, or commitments at the same time – meaning you can’t give enough attention to any of them.
The phrasal verb “wrap up” means to finish or bring to an end.
Saying something needs to be done “yesterday” is an informal way to say it needs to be done VERY URGENTLY, as soon as possible – as if it were possible to travel back in time and finish the task yesterday!
– See more at: http://www.espressoenglish.net/5-english-phrases-and-10-idioms-for-complaining-about-your-job/#sthash.wBKGwFtX.dpuf