Here are some corrected versions of your sentences:
- They do their best to sell you the idea that you are working in a modern, innovative organization, while the reality is that they are merely putting lipstick on a pig.
- The work environment is very demanding; they do not pay well but still expect you to be the perfect employee who is always striving to improve.
- They cut pay like crazy over anything, and the managers are very passive-aggressive, although they try to seem nice at first."