It's fine to shorten but only when the reader can fill in the blank.
So far, you have:
Managing a lot of people is a very difficult problem
people, difficult problem
In this example, you have 3 concepts:
- It's about managing people
- There are a lot of people
- It's hard
The most important of these is the first, that your article is about management. Yet it's the one you dropped in your title revision. "Lot of people, difficult problem" can be about anything. Even if you know from context it's about a workplace (and not about, say, overpopulation), it could be about noise levels or fitting in enough desks/cubicles or the fact that you don't have enough bathrooms. All those can be legit articles about work.
I would drop the third concept, that it's hard. Because that is implied by the fact that you are dedicating an entire article to it.
This leaves you with:
Managing a lot of people
It's a boring title, but it's got all 3 concepts in it (the 3rd is implied). And it's half the length of the old one.
I'll leave it to you to make the title more interesting, and more focused (since you're presumably not covering everything about managing multiple people), because the job of Writing.SE isn't to rewrite for you. Instead, it's to help you work through it.
What are the concepts you are trying to convey? Which are the most vital? Which can be dropped because they're implied? Which can be dropped because they're unnecessary in the title?