There is no exact definition of "chapter", this is very much up to the author to decide. For myself, I consider it the first chunk of continuous time the reader will see, in the life of the main character (MC). Or fairly continuous; I will still leave out time-consuming bits that slow down the story; like sleep, travel, washing up, getting dressed, cooking or eating or using the restroom. Not out of any modesty, they just aren't actions important to the story.
The first chapter can be difficult because it has several jobs. But the MAIN job, in my own writing, is to introduce the main character and get the reader interested in her life.
Other authors begin with a setting, or begin with characters tangential to the main character: JK Rowling opens her first Harry Potter book, not talking about Harry Potter, but his aunt and uncle that will raise him, Mr. and Mrs. Dursley: Proud to be perfectly normal. But on page one she introduces their secret, and fear they will be associated with the Potters, and found out to be not normal at all.
In the next few pages we start seeing elements that will all turn out to be magic (owls, a cat reading a map), but Harry is still not mentioned until page 5. Nevertheless, by the end of the first chapter (page 21), we see plenty of magic, and have some clue about the central conflict for Harry, discovering who he is. (Yes, Voldemort killed Harry's parents, couldn't kill the infant Harry. But to me the central conflict is that Harry was left on the Dursley doorstep to be raised by them, doesn't know his magic nature, and will "come of age" in the magical sense at 11 and discover a new self and a new world of wonders in which he belongs).
The next chapter starts ten years later: To me, that passage of time is the hallmark of a chapter break; the first chapter covers a mostly continuous single day, then there is a gap where whatever happens is inconsequential and left to the reader's imagination, or just sketched in writing (for example, "Her cab arrived and she left for the airport, and London." End of chapter. Next chapter, she's been in London for days.
In your first chapter, I feel you must introduce your world and your hero and something about their problem. If there is magic (or technology that might as well be magic) you need to make that firmly known. All of this intertwined in some way, so it feels like a story: a character with a problem moving through a setting.
This is made more difficult by the fact that readers don't know anything yet about your character or setting or anything else.
To address that writing problem, you need a device; an excuse to start telling somebody this story about a stranger in a (presumably) new and fictional setting (whether or not your story is a realistic modern day setting).
However, readers know this, and will give you several pages of leeway to get your story engine going, the first page at least if no glaring writing errors are present.
The device you need is conflict; in a very broad sense: To me, 'conflict' is anything that my hero has to deal with and cannot ignore, from pouring soured milk on her cereal, to full lethal battle with the bad guys.
However, for the first chapter, I think it is a mistake to jump into major conflict because the reader doesn't know anybody and therefore has no sympathy for anybody, so major conflicts will fall flat. They won't be exciting, because the reader doesn't know who to root for yet, there is no context or lens for them to see this scene through.
For that reason, I typically start my hero off with a minor conflict, I call it a "throwaway", meaning a problem that may not really influence the plot. It can have influence, or be foreshadowing, or cause the hero to do something out of the ordinary: Like waking up with the power out, finding yourself late for work, and taking a different train in to the city, and meeting somebody on it that IS important to the plot.
But it doesn't have to; it is just a device, a problem you can describe your hero dealing with, that shows us something about her, something about her world and situation, and creates sympathy in the reader for her. They don't know everything about her yet, or about her world, but you hit some big points so the reader is grounded in your story.
By the end of the first chapter, the time break, you should have reader interest in seeing either how something turns out, or at least following this character into Chapter Two to see what happens to her next. For me, all my heroes are rare in some way (like Harry Potter is), and that promises the reader that by following her, they will see new things.
You have heard of page-turners before: The essence of entertainment in reading is anticipation and wanting to see what happens next. The story is a chain reaction of teasing and fulfillments; each time we find out what happens next, this should create another anticipation of ... what happens next?
Until the finale, in which what happens next is no longer a big question; for a happy ending our hero is safe and going on with her new life.
IMO: What you need for the first chapter is a minor problem you can use to introduce your character, her world, and perhaps a larger problem for the reader to wonder about, so we can care about her and want to see what happens next.