guys i wanna ask , in prometheus when we see the goo going on the floor and touching the worms, does that mean the worm turned into the parasite we see later like a snake like parasite??
Yes. the worms seen in the soil are indigenous to the planet... and they mutate into the snake known as the "Hammerpede".
and who created the engineers? and why did they need to create an alien lifeform
Nobody knows where the Engineers come from, but their creation of alien life forms is kinda like when Charlie and David are talking, and Charlie says humans made David "... because we could".
David's response is "Imagine how you would feel if the Engineers said the same thing about why they created humans"
and how did they make the goo??
Charlie, Fifield and the worms were all mutated after they had come into contact with the fluid.
In terms of Charlie and Elizabeth, they had sex after Charlie had been (unknowingly) infected... and the "child" Elisabeth has is a mix of hers and Charlie's DNA, resulting in the "Trilobite".
That Trilobite then impregnates the Engineer, which in turn results in a Xenomorph looking alien called a Deacon.
What's interesting on this as well, is that Elizabeth is actually infertile, showing the power of the black fluid.
In short though, it's revealed later in the film that the black fluid is a biological weapon, and also the Engineers' way of creating life... and it mutates anything it touches and has the ability to create and mutate life depending on how it is used.
At the beginning of the movie, we see an Engineer drinking some of the fluid, which breaks down his body/DNA, and fertilises what is essentially a barren planet.
The fluid he drank was probably engineered to do that very thing, whereas the fluid in the ship that infects the worms, Charlie and Fifield was probably raw and untreated which is probably why it reacts in such an uncontrolled and random way.