Questions
1) Do you think magic that all could use would slow down even halt technological advancement
It really depends on your magic system and your setting. If magic is all powerful and without limits, then its possible. However, if magic is bound by rules, then I would say probably not. Also, in your setting, there may be individuals who may not have access to magic for one reason or another. In those cases, the individuals would advance technology to keep pace with the advances in magic. In the Sword of Truth series, Zedd points out that in warfare, magic is ultimately pointless if both sides have it. One side will attack with something, and the other side will figure out how to defend it making that attack worthless. It may work for a while, but won't work forever. The same can be seen in the real world with technology. Look at the advancement of weapons and armor in the middle ages. As armor technology got better, weapon technology got better to get around the armor, thus causing armor technology to evolve again. Ultimately, I would say magic would advance technology quicker then without it.
Questions
2)Magic vs technology who would win? let me expand say modern or maybe ten years into the future technology compared to earth. While the magical society has less people but is very adept with elemental magics.
"Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke
"Any sufficiently analyzed magic is indistinguishable from science!" - Unknown
Advanced technology can do things that might seem like magic to those who don't understand how it works. In sci-fi, you see concepts of things like FTL, futuristic weapons, or even tricorders. When those concepts were first invented, the writers probably had no idea how they would actually work and didn't need to when writing the story. However, as technology advanced, we have figured out theoretical ways or not actual working prototypes of how some of the stuff works. The biggest issue with technology is that it is limited by the laws of the universe. If your magic is also limited by these laws, then it's a question of which one is more advanced. If magic isn't limited by these laws, then magic is clearly the winner.
Questions
3) Can magic advanced society and technology advanced society work together well?
3.5) If yes what are problems each would have with each other?
If the leaders involved are smart enough and/or the situation is needed, they can work great. There would probably be a lot of interchange between the 2 societies about how their stuff works assuming magic and technology would work in both societies. If so, then the outcome would probably be even more advanced societies with both magic and technology working together.
If the leaders involved are dumb, its very possible we may end up destroying each other.
Questions
4) If you found out one day that magic was real and there was a whole society from a different world who sent representatives to earth to give a warning of an impending war from a society who had advanced in technology and magic equally and an alliance between earth and the representatives home world waa the only way to survive.
See answer 3.
Questions
5) Am I making this to complicated?
It is an interesting problem that can have many points of view. As such, delving into the possibilities can make for an interesting story. In Brandon Sanderson's Mistborn series, you can see examples of different magic systems competing against each other, and in Alloy of Law specifically magic being used in conjunction with technology. Brandon Sanderson's magic system in the Mistborn series is, to use his term, a Hard Magic system. It has specific rules and limitations, and to that extent is basically a different form of technology.
Overall, the real question is, what will the people who control the magic and technology do with it?