Since most of your story is about doing the activity with your friends, I would suggest that you not start the paragraph with “You start walking alone... “ It suggests that what is to follow will be about a solo journey.

I changed a lot of your commas to periods.  It makes it much easier to read if you write shorter sentences.  With commas, I am trying to link everything together and I can’t stop to breathe. Periods give those breathing spaces. I had a teacher who said to read what you wrote aloud- if you had to pause to take a breath in the middle of your sentence, your sentence was probably too long (I got corrected on this alot because I like longer sentences. – Really that last sentence I wrote should be split after “aloud” and I should start a new one with “If”)

It sounds like a wonderful trip!   

A little discussions starts on the beauty of the landscape beauty, but we are still far from the refuge, and it is time to put return the camera in to the backpack to put back ,(you could also say here: to put back the camera in the backpack, but the repetition of back is not pleasing to the ear... this is personal preference though – both would be correct)You drop bend the your head and leave start again, moving towards the next stop ....

After some time awhile you stop to walking, to reformer the group, .Waiting for all of the walkers, you take your water bottle and take a drink to refreshed you.Everyone comes, puts her bag down and does the same thing: drinks and eats dried fruits in anticipation of hours of walking ahead.Someone takes the camera out of her backpack to freeze capture the group portrait landscape (here- are they taking a picture of people (portrait) or of the mountains (landscape)? I assumed people since you had added the word ‘group’).

You start to walking alone or with your friends,

 you start the ways to look for shelter of from the sun under the trees, and everyone is excited, discussing the exploit together. (this phrase I changed quite a bit. I hope that I retained your meaning. I was unsure of your use of the word discussions twice...)  the discussions on the everyone exploit discussions going well, You go up without being too tired, and after another turn the forest disappears, the way disappears, giving the way for to a one stony byway.,The slope increases, and the discussions are finished.Faces begin to drop, the and sweat begins to bead on the fronts everyone’s forehead.,  Between each walker the space increases and , the hierarchy is established.Each takes  You establish your (I changed pronouns here to match what you had written elsewhere)his walking pace, you lift your head from time to time occasionally to see how the path ahead in the mountains, and from time to time you look behind you. and You begin to see the beautiful scenery.