In a bid to reduce population, the dead are allowed to live again virtually, and when it becomes illegal for living people to post their opinion online, billions commit suicide while others risk their lives.

As the previous commenters have said, you have only set up the world. With more consideration for word real estate, this could be phrased as:

"In a world where an online afterlife has made suicide enticing for billions..."

Then, you are missing all 3 elements of the formula: EVENT, CHARACTER, and ACTION.

Re the world, you may want to check the graphic novel Elysium Online by the Greek comic artist Ilias Kyriazis: https://www.goodreads.com/en/book/show/18753600-elysium-online#

This idea has a logic problem,

If people don't die; but become 'undead'

The population of the earth would rise dramatically

As mikepedley said.? I think you have an intriguing premise, but it needs a specific plot, one focused on a singular protagonist.