You know what? Somebody should have gotten back to you with at least something. I don't have time to do more than the first three paragraphs, but let's get you SOMETHING feedback-wise.
And, the main thing I'm going to suggest is getting rid of paragraphs 1 and 2.
That said, let's look at paragraph 1 for a moment. It's a decent opening paragraph. It's doing a lot of things right as far as setting a tone of melancholy for a lost past. You do, however, fall into the usual new writer thing of a somewhat tepid opening sentence followed by a much better sentence that should have been the opening in the first place. That said, this shouldn't be your opening sentence at all.
Paragraph 2 is pure infodump. And, it doesn't need to be there. Everything in it is information that can be drip-fed to the reader to better effect later in the narrative or through dialogue. A good general rule when it comes to world building is that it is better to show the reader a little bit at a time through the eyes of the POV character than it is to front load information and hope the reader retains it.
And now, paragraph three. This paragraph makes for an amazing starting point for your narrative. Imagine, for a moment, that all the reader has at the start of the story is "Day 68" and the third paragraph. Where does this leave the reader? They know it's day 68 of something, and the narrator is trying to sneak into their own house. There are so many unanswered questions, and they are ALL interesting. With this mystery, and all the questions that arise as a result, the reader is propelled into your narrative in a way that wouldn't be possible if you told them up-front "the world has been destroyed by monsters."
Another way to think about this is to consider the first Resident Evil movie. The movie starts with a quick scene of somebody releasing the T-virus in an underground lab, and the computer going nuts and killing everybody as a result. Remove that quick scene, and what you're left is the computer killing everybody for reasons unknown. All of a sudden, the movie would have a compelling central mystery that it didn't have before...all because of that little bit of information being withheld from the audience instead of being shown.