The search for the unknown, could be a blessing or a curse, but the fact is, thanks to thait, humanity can progress and reach aaccomplish a great many of achievements,: go to the mMoon, control the fire, develop the internet, make airplanes, cars, ships, the gGreat wWall of cChina, the 7 wWonders of the wWorld, a. All of them, has ave the purpose tof showing our maximum capability.

(1) "The unknown" is a general term that refers to anything that is unknown to us. Similarly, we use phrases like "the elderly", "the Spanish", "the rich", etc.
(2) The placement of the first comma breaks the flow of the sentence.
(3) In the phrase "thanks to that", "that" refers to the FACT that the search for the unknown could be a blessing or a curse, rather than the search itself.
(4) We do not use "reach" with "achievement". You can use "accomplish" instead.
(5) "A many of" is not grammatical, but "a great many of " or "a good many of" is.
(6) One function of the colon (":") is to provide elaboration. Since things like going to the Moon and controlling fire are examples of achievements, they are elaboration. A colon is appropriate here.
(7) When referring to the Earth's moon specifically, we use the capitalised word "the Moon".
(8) You're referring to fire in general, rather than a specific fire, so omitting "the" before "fire" sounds more natural.
(9) The "Great Wall of China" is the name of a place, and is capitalised.
(10) The "7 Wonders of the World" is the official name of a list, so it is also capitalised.
(11) I think splitting this sentence into two would be more appropriate here.
(12) "All of them" is plural, so you should use "have" and not "has". You would use "has" with "each of them" instead.
(13) Rephrased the last part of your sentence so it sounds more natural and fluent.

However, there exists one specific question which always makes scientistscientists will always ask themselves,: is it possible to have extraterrestrial life?

There have been reports of UFO sightings, abducted humans, the mysterioues around Area 51 eand the secret experiments fromby the government.

(1) "Mysterious" is an adjective. "Mysteries" is the (plural) noun.
(2) Experiments are conducted "by" someone, not "from" someone.

Besides, we have one in specifictheory in particular which could give us a possible explanation.

(1) The subject of this sentence is missing. You can use "we" here.
(2) You should specify what it is that we have one of. In this case, what we have is a theory.
(3) "In specific" is not a phrase we use. The correct expression is "in particular".

Let me introduce: The theory about the dark Fforest from FarmI Ptheory from the Fermi paradox.

(1) You are not beginning a new sentence, so "the" shouldn't be capitalised.
(2) The theory is known as the "dark forest theory" or the "dark forest hypothesis".
(3) The paradox is known as the "Fermi paradox".

Goingetting (straight) to the point, the theory say what: Ifs this: If there really exists others societies, coming tofrom outside, why have themy not showed up forto us?

(1) "Go to the point" is not a natural expression. The phrase is "get to the point".
(2) "Other societies" is plural, so you should use "exist" and not "exists".
(3) You can omit the first comma. I think it breaks the flow of the sentence.

“Shoot first, ask later” maybe, but revealing our position could be really dangerous’ w. We don't know how advanced the technology they could have, if is, or whether they are hostile or not, so many asks and c, so we have many constant questionst antlyd doubts.

(1) I think the addition of a contrast-establishing word like "but" makes this sentence flow better.
(2) "Ask" as a noun refers to a request or the act of asking. The noun to use here instead is "question".

Maybe it can give us an explanation about why so far, wes to why, until now, we still don’t have any contact coming from outside.

"As to" is a phrase meaning "with respect to; concerning". It sounds more natural than "about" here.

But, still rest one question, and if… still remains: If...we are alone in this colossal universe, were were the only society whichthat evolved andwhile the others werent extinct?

(1) "One question remains" is a fairly common expression.
(2) "We were" is a structure used in statements while "were we" is used in questions.
(3) The explanation of the difference between "which" and "that" might be a little lengthy. But to simplify, "which" is used to bring in information that is not as important, while the opposite is true for "that". "That" would be more appropriate here.

I honestly don't know, both scenarios seem apocalyptics.

For now, we are safe,; only time couldan give us an answer.

(1) You can use a semicolon here. Alternatively: "For now, we are safe, and only time can give us an answer." Both are okay and flow more smoothly.
(2) Instead of "only time can give us an answer", a fairly common expression you can also use is "only time will tell".