There are actually several different issues with the proposed statement which need to be addressed:
"Human first" vs. "Humans first"
The first question that comes to mind when reading "human first" is "which human?". Is only one human being put first? If the answer is yes, then you probably need to specify more precisely which one:
"Put that human first," said the robot overlord to the executioner.
The answer is probably no, though, and you really meant to put all humans first, in which case "humans" needs to be plural here:
The angry mob shouted, "Humans first!"
Is "humans first" a valid sentence?
No. There is no verb here, so you can't just use it by itself as a sentence. A proper sentence should say something like "Humans should come first."
It is common in some circumstances (slogans, headlines, etc) to leave verbs out of sentences when the meaning can be understood without them. This can be done for emphasis or convenience (when chanting a slogan), or to save space (when writing on signs or printing newspaper headlines). It is also sometimes done in advertising. It's important to note, however, that while this is common, it is still not grammatically correct, and should not be done in more formal contexts. A more correct way to write your text would be:
Humans should come first. We prioritize human development, because we love our job. Customer satisfaction starts with our own work happiness.
Period vs. Colon
Using a period to separate the first sentence from the rest of the statement is technically OK, but since the first bit is serving as an introduction to the rest of the text, arguably a better choice here would be a colon:
Humans should come first: We prioritize human development, because we love our job. Customer satisfaction starts with our own work happiness.
When to use hyphenated phrases
Regarding "humans first" vs. "humans-first", connecting words with a hyphen changes them into an adjective (or sometimes an adverb), which means they then need to be used to describe something else:
We believe in putting humans first.
("humans" (noun) are being "put" (verb) "first" (adjective))
We have a humans-first attitude.
("humans-first" (adjective) is a modifier of "attitude" (noun))