Could a native English speaker correct the mistakes in this text and make it sound better?Thanks in advance.?

Not much needed to be changed, it was good. See what I've done below.

The central premise of this novel is the return of two people who have been away from home for a long time. Upon arrival, they both feel that they are alienated from their hometown. All memories of their chilhood and adolescence are gone and have been replaced with newer ones. Old pictures, diaries, houses and alleys are almost meaningless, because if you are leading a new life in a quite different place, memories easily fade away unless they are fed by constant reminders. The thing that keeps the memory vivid is to keep it fresh through reciprocal relationships with your family.

The return of two people who have been away from home for a long time is the central theme of the novel. When they arrive, they both feel that they have become alienated from their hometown. All the memories of their chilhood and adolescence are distant, having been replaced with fresher ones. Old pictures, diaries, houses and alleys are now almost meaningless, because while you are leading a new life in a quite different place, memories are easy to fade away, unless they are fed by surroundings reminding you of them.The thing that keeps the memory vivid is to constantly refresh it with reciprocal contact with relatives and friends.

Hope this helps!

Without knowing what you trying to say.......

The return of two people who have been away from home for a long time is the central premise of the novel. When they arrive, they both feel that they are alienated from their hometown. All the memories of their childhood and adolescence are gone, being replaced with recent and fresh ones. Old pictures, diaries, houses and alleys are almost meaningless. Because if you are leading a new life in quite a different place, memories fade away easily unless they are fed by the surroundings that remind one of them.The thing that keeps the memory vivid is to refresh it with reciprocal relationships with your folks

The return of two people, who have been away from their home for a long time, is the central theme of this novel. When they return to what was once familiar surroundings, they both feel a sense of alienation from their old hometown. All of their childhood memories and those from their adolescence are gone, needing to be replaced with more recent ones. Old pictures, diaries, houses and alley ways, all seem meaningless to them. Once you've begun a new life in a very different place, the memories of what once was, can fade quickly away unless one is reminded by people or surroundings from their past. The thing that can help hold memories intact, is to keep them alive, through ongoing relationships with family and friends from that time frame.

Pretty good all ready. Only a couple of awkward places, and also, some things I'd simplify.

Upon their arrival, both feel alienated from their hometown.

All the memories of their childhood and adolescence are gone, having been replaced...

The four examples of pictures, diaries, houses and alleys don't seem to go together. I'd keep it either four inside things, or four outside.

...because if you are leading a new life in a different place, memories easily fade, unless fed by familiar surroundings.

What keeps the memory vivid is to keep in touch with those you love.

This could be done differently, of course. Just my quick thoughts.

"chilhood" needs to be "childhood"

I'd put a period after "meaningless," leave out the word "because," and capitalize "if." The sentence as it currently stands qualifies as a "run-on" sentence, and those changes will break it up a bit.

I'm not editing the sentence for style; that part is up to you.

Beyond that, it sounds fine; it's already grammatically correct outside of the single spelling error. Nice work :-) I know plenty of native speakers who couldn't do as well, sad to say.