When we read Gen 1 creation account we see 3 days of God separating, 3 days of God creating and 1 day of God resting. The creating days start on day 4 starting with the celestial objects, the birds and marine life then finally land creatures concluding with man. All these living creatures are in the singular in Hebrew yet they are all translated as not as a simple male and female pairing or a single specimen but mass nouns.
Then comes man. Some translations say "humans" some say "mankind". The Hebrew is "adam" but like all Hebrew names they are first Hebrew words with real meanings and "adam" is the word for mankind. So why in v26 do we assume male and female only (or just 1 man) but in the rest of the entries we assume mass nouns (birds, fish, animals etc..)? If Gen 1 was looked at in isolation when God creates man he creates an entire species that populate the world which would be the most consistent in the context.
Gen 1 opens in 1:1 and it closes in Gen 2:1-3. These are bookends to the creation account then starts a new account opening with a different focus in v4. Gen 1:1 says "In the beginning, God created the heavens and the earth..." and Gen 2:4 flips the focus saying "This is the account of the heavens and the earth when they were created, when the Lord God made the earth and the heavens." it opens with "heavens and the earth" and closes with "earth and the heavens" which may suggest Gen 1 has more of downward perspective and Gen 2 may be more of an upward perspective which is a common tension in scripture (ie. was Pharaoh's heart hardened or did he harden it himself...? scripture says both). This points to Gen 1's creation as a separate account from Gen 2's creation which would make sense with the inconsistencies the two present such as the order of creation or the different word used for "God" when juxtaposed together.
So according to Gen 1 should "adam" be a mass noun as it is commonly translated such as "humankind" or should it be in strict singular form going against the rest of the creation account?
He created on all six days. "In the beginning, God created the heavens and the earth."
Day One
He created Earth. It goes on to describe it being formless and void, with water, just like a floating bubble, like a lava lamp. Evidently since there was no stars, planets or moon yet with the physics, gravitational forces, it was a basic lump that He then worked on. He created light on the first day as well - this was light that was a physical light with waves, particles, the color spectrum - very complex, but notice it did not come from the sun, created on the 4th day. It radiated from Himself onto a physical earth.
Day Two
Separating the waters, was an act of creation as well, our breathable atmosphere, the clouds, the upper atmosphere, a protective barrier from space and this of course involves gravity.
Day Three.
He gathered the waters onto seas rivers and lakes and allowed dry land. And then created all the botanicals.
Day Four
Sun, moon, and the rest of the universe.
Obviously the botanicals could not survive too long without the sun. This proves 1 day equals 24 hours, not epochs of time.
DAY FIVE
Sea life of all kinds.
Day Six
Animals of all kinds and finally Man.
Notice, God finished all His work by the end of the sixth day. Therefore, all events, order and creation of Eve in chapter 2 are details about the first six days.
Day Seven
He rested
What you seem to be confused about is the style of writing. The Hebrews have a style of outlining their thoughts, introducing the basic information in a paragraph or chapter first, then going back and filling in the details in the next paragraph or chapter. This is what Genesis 2 is, details about Genesis 1.
You will see this style throughout the Bible.