If you actually cared, and you're older than teenaged, you'd already know.
We get this kind of thing from the creationists regularly. They ask questions that they don't care about the answers to as gotcha, the implication being that if the question hasn't been fully answered, that somehow that translates to support of creation by their god.
The proper way to learn the science is from books or websites dedicated to teaching science such as Talk Origins. If your interest is sincere (and if it is, congratulations, that makes you the first creationist I've encountered that is), go to this Google search and read the first dozen entries, take notes, and return with any questions you have about that material:
the origin of the sexes in evolution - Google Search
But first, learn what sex means in biological terms. It's not what you seem to think. Then learn about the evolution of genetic transfer between microorganism, learn what a gamete is, what haploid and diploid mean, what meiosis and reduction division mean, and learn the evolution of sexual specialization (gamete anisotropy).
That's not going to happen, is it? And why? For the reasons suggested here. The creationist isn't interested in the science, which is why he almost never knows any. There are many of us here who are interested in science. We have always been. As kids we had chemistry sets and erector sets. We sat glued to the TV for space missions and watched the science for children shows. Later, we subscribed to Scientific American or Sky & Telescope. We ate up the biology, chemistry and physics in high school. Many chose the sciences professionally. Most continued reading after graduation, which is where I learned the science I didn't learn in my formal education (earth science, quantum science, cosmology). That's a typical story for people interested in science, and it's why such people can answer your questions or find the answers.
There's a reason you don't do either of those. You aren't interested. As I said, if you were, you'd already know what there is to learn on the matter, or, if you're still in grade school, you'd be taking up the offer to dig into the literature and bring your insights and questions back here. As I said, that just never happens in these discussions, so I've learned not to take these requests from creationists as inquiries, but as implicit incredulity fallacies - you don't see how sex could have evolved so it didn't, therefore God.
Another thing to notice about creationist apologists is that they don't discuss the merits of creationism, just what they see as flaws in evolutionary theory. Can you provide an argument for biblical creationism that addresses creationism itself rather than trying to disqualify the science with gotcha "questions"? The argument for evolution doesn't address supernatural creation at all. There is no attack of it, rebuttal of it, or even mention of it. Try that with your hypothesis. Tell us an argument for creationism that isn't an argument against science.
That's not going to happen either, is it?
One more thing that no creation apologist will address. I've asked this rhetorical question dozens of times on RF, and not a single creationist has addressed it, which I think speaks volumes:
Why would I or anybody else trade a scientific theory that unifies mountains of data from a multitude of sources, accurately makes predictions about what can and cannot be found in nature, provides a rational mechanism for evolution consistent with the known actions of nature, accounts for both the commonality of all life as well as biodiversity, and has had practical applications that have improved the human condition in areas like medicine and agriculture with one that can do none of that and can be used for nothing even if correct?
Do I need to say it? You can't give a good reason, and if you try, you will be the first.
Pseudo-science tells, that the first life in Multiverse was primitive one-cell organisms.
The only pseudoscience in this thread so far is that comment. Science says no such thing. It doesn't acknowledge that there is anything outside of our universe (it admits to the possibility, but doesn't make the claim), nor does it comment about extraterrestrial life except to speculate that it may be out there and suggest ways to detect it if it is.
This is what I mean about creationism apologists repeatedly bungling the science. Why don't you know how ill-formed that comment is? Another rhetorical question needing no additional answer. It's answered above. You never cared enough about the subject to get the proper foundation necessary to avoid such mistakes.
This cannot be a million years-long evolution
Of course it can. But I suspect that you have some model of sexuality appearing when some asexual creature somehow produced male and a female offspring, some sort of irreducible complexity idea that there are no intermediate steps available to evolution to make the transition over eons of geological time.
Anyway, here's wishing you great success in your program of independent science study, your argument for creation that isn't a misrepresentation of science or even mentions science, and for explaining why one should replace a successful and useful scientific theory for a religious story that has no predictive value even if true. Make me wrong and do those things if you are sincere about learning the science, in this case, the evolution of sexual reproduction.