Please imagine the embryology.

However, “life” itself is against the nature.

I would like to write about my first experiences.

Please imagine the embryology.

It becomes a fish-like form, then an amphibian (frog?)

), a bird (chicken?)

),and then a mammal (animal?)

), and fFinally, it becomes atakes on the human form.

We have always experienced these first things even after we weare born into this world.

For example, we can stand up and walk for the first time around when we are one year old after we come out ofinto this world.

And we lie on a bed and can't walk for the first time in the future when it's time to say goodbye.

However, “life” itself is against the nature.

For example, we are inhaling Ooxygen and exhaling Ccarbon dioxide every moment.

The people who think about SDGs consider that thecarbon dioxide emitted by cattle’s CO2 is the problem of SDGs.

However, why don’t they saytalk about carbon dioxide created by human CO2s?

So, I think the ultimate eco-friendly, SDG is to reduce the population of the earth.

The population of the earth will increase and make a peak around 2050, then after leveling off, it will start to decrease from around 2100.

Please imagine the embryologybeginning of life.

If we used embryology it would mean "Please imagine the study of the development of an embryo from the stage of ovum fertilization through to the fetal stage." I don't think you want people to imagine a whole branch of study. My guess is you want them to think of what is being studied, not imagining the study of what you're studying. If that makes any sense.

I think any of the following sentences would make a little more sense.
"Please imagine the beginning of life"
"Please imagine the fertilization process"
"Please imagine life before becoming a fetus"
A more poetic way might be
"Please, imagine for a moment, before you were born, before you were a fetus in the womb"

ItThat cell becomes a fish-like form, then an amphibian (frog?)

"That cell" rather than "It" helps clarify what is turning into a "fish-like" form.

), a bird (chicken?)

minor punctuation corrections

), then a mammal (animal?)

minor punctuation corrections

), and finally it becomes a human form.

minor punctuation corrections

We have always experienced the first things even after we were born in this world.

I am not entirely sure what is meant here. It could be interpreted as "We have always experienced firsts even after we are born in this world."
"Firsts" in this case tends to refer to all of a baby's "Firsts" so first steps, first words, first sentence, etc. I don't know why we omit "things" in there, but it's generally just referred to as "Firsts" like "baby's firsts"

For example, we can stand up and walk for the first time around when we are one -year old after we come out intof this world.

Minor punctuation correction, saying "out of this world" implies we are no longer in this world, to say "into this world" implies that we have entered this world.

And we lie on a bed and can't walk for the first time in the future, when it's time to say goodbye.

minor punctuation helps break up the sentence making the meaning a little more clear.

Everything in nature moves to increase entropy, but "life" moves in the opposite direction.

Life doesn't need to be in quotes, if you would like a greater emphasis on life, then capitalizing the L in "Life" works better. That might be subjective.

However, “life” itself is against the nature.

Life doesn't need to be in quotes, if you would like a greater emphasis on life, then capitalizing the L in "Life" works better. That might be subjective. "Nature" is a more generalized term, saying "The Nature" is more specific, like "The Nature of Mankind" or "The Nature of that breed of dog" by saying "Nature" without "the" tends to imply more of a "Mother Nature" type of nature.

For example, we are inhaling Ooxygen and exhaling Ccarbon dioxide every moment.

Chemicals such as "oxygen" and "carbon dioxide" do not need to be capitalized unless they are the first word in a sentence.

The people who think about SDGs consider that the cattle’s CO2 is the problem of SDGs.

Looking up SDG I'm seeing "sustainable development goals". I recommend to either be more specific about which of those goals cattle's CO2 is harming and rather than say "the cattle's CO2 is the problem of SDGs" I would say "the cattle's CO2 is one of the problems harming this goal" with "this goal" being whatever specific SDG goal you are referring to. Also if you aren't referring to "sustainable development goals" then I'm not sure what you mean by SDG.

However, why don’t they say that about human CO2?

"that" here helps clarify that you're asking why aren't people saying that human CO2 is a problem as well.

So, I think the ultimate eco-friendly, SDG solution to reach the SDG goal is to reduce the population of the earth.

Minor punctuation correction.
It doesn't define what is the ultimate eco-friendly is, it could be a person, product, plant, so I clarified it by adding "solution to reach" to show that you are talking about the ultimate eco-friendly is referring to a solution that will help reach the SDG goal. I added "goal" because while it is redundant to have the word "goal" in the acronym as well as a word added on the end, since we aren't hearing what those words represent, it sounds odd without the "goal" word.

Jonathan Swift wrote in his article, ”A Modest Proposal” that the Irish should eat their babies to survive in the famine.

Minor punctuation correction.
"survive in the famine" makes it sound like the famine is a specific place/area/location rather than a natural disaster. I would say "survive during the famine" or "survive the famine"