Your story is interesting. You've written it in first person. I'm not against it, but you seem to know how limiting it could be to not have a third-eye view of the situation. More intimate with the characters, but less understanding of the overall situation objectively. Win some, lose some. That's fine.
One thing to note is the occasional grammar check for dropped words and capitalization:
At the end of the blade my dear brother's hand.
"Where am I. where's Brad?"
and for mistyped punctuation, like here where it's likely to be two sentences:
I had started my first job at a garden center, but I had always been a weak kid, skinny, with pale skin, I always preferred burying myself into books instead of getting involved in sports
I like the intro to your story. Just the title itself foreshadows what's about to happen. Unfortunately, the meaning to the title of your story happens almost immediately into the chapter. I, personally, think I like chapter titles with meanings that are revealed later on in the chapter, like maybe around halfway. No biggie here.
One technique you can play with: manipulating word amount and text spacing to correlate with time or distance.
Here, you originally have:
I took off running faster than I ever had before. I could see his silhouette about 50 meters in front of me. 30. 20. 10. "BRAD!!!"
You could play with the spacings and the amount of words, and do something like this:
I took off running faster than I ever had before. I could see his silhouette about 50 meters in front of me.
30 meters left.
20 meters.
10.
"BRAD!!!"
You'll achiever a sense of "stretching out the time/distance" that you wont with a 30. 20. 10. "BRAD!!!" in one line. That single line of information gives a sense of "happening very fast" due to the eye scanning it all at once, which might be opposite of what you wanted to portray here. By breaking it up into multiple lines, although short, they forces the eye to reconsider the information given, and if you play with the amount of words you feed out, the readers can visually see that it gets shorter as he approaches his target.
Now, back to your story arc. Great beginning. Good hook, great presentation. You didn't flat out say, "I was happy", but utilized your emotion thesaurus! Good job there.
You didn't flat out say, "Hey, I reincarnated 10 years to the past!" either. I like how you fed that information in slowly.
My biggest thing, though, about your story, is that information dump you did right before your chapter ended. It was going so well too, until that wall of text popped up. You can literally take all that out, and it'll still be a great chapter, I believe. All those information seems like it can be slowly disseminated throughout your story. You can even keep it brief like this:
I couldn't help but recall how all of this started, of how the Large Hadron Collider ripped a portal open to a planet in another universe A planet completely different than the one we had known.
This place was called Agartha.
I sat for a moment and collected myself. After doing my best to adjust to my new reality, I looked up at Mike and said, "My bad bro, let me get ready."
It still works too. I'm a big fan of the "learn as you go" method of world-building.
But all in all, you have great hooks. Great reels too.
Hooked into asking why would Brad make that decision? Why did Troy end up going back? What happened to Mike? He sounded like a good-nature guy, so how did Mike die? Did he sacrifice himself for Troy to survive?
Chapter 1 here didn't reveal much, but it also didn't say much about Brad either. I understand that our main character (MC) searched for his brother for 10 years, but why is nothing of it mentioned again in post-reincarnation besides the "where's brad?" It seemed to be a powerful motivator, but it was lost briefly in the second part of your chapter.
10/10 would recommend chapter 1.