this is such over rated movie for pseudo intellectuals and nerds

They explained all of that. The aliens came to our world to teach humans their language. By understanding their language, one also sees time in a non-linear fashion and that's why Louise is the one who can see into the future. They gave humans this as a gift, but also because the use of this gift would allow humans somehow to aid the hyptopods in 3000 years when their species was in trouble.

It was a great journey to go through with the characters, emotionally intense and beautifully shot, however I have learned nothing from this movie and it actually left me with many questions. I still don't understand why the aliens came. To give them their language? To create world piece? What was so epic in their arrival? I like the twist with her being able to see the future I actually was shocked when she said who is this child? However I really was expecting something big to happen.

One of the most disappointing movies I have ever seen. An extremely badly told story, with minimal entertainment value or educational value either. Not helped by some amateurishly mumbled, incomprehensible dialogue.