nA Near-dDeath eExperience

We capitalize the first letter of important words in titles.

Once upon a time, my family and I went inton a mountain tour.

That mountain is around 200 meters at the tophigh, but luckily we did not go toovery far.

As I remember, the sight was very greatbeautiful and the nature was peaceful there.

We did normal things, as a normal family would do up there, w. We took some pictures, selfies, and breathed fresh air (otherwise we would be dead hehe).

This is better in two sentences.

We were at a very high point when this happened, so m. My family and I were going down the mountain from the stairs that are up there, but mey kiddo decided to go down by jumping each step, t. The result is very obvious.

I slipped down ion the next to the last step, I rolled down and I almost fell out fromff the mountain.

Beware of your steeps ...

nNear-death eExperience

capitalizing titles

Once upon a time, my family and I went inton a mountain tour.

for tours, it's usually the preposition "on" as in: went on a tour

That mountain is around 200 meters ato the top, but luckily we did not go too far.

AsFrom what I remember, the sight was very great and the nature peaceful.

We did normal things, as like a normal family would do up there, - we took some pictures, and selfies, and breathed fresh air (otherwise we would be dead hehe).

haha true
breath is a noun, breathe is a verb - breathed for past tense

Everything was just pure happiness, until something happened...

usually an adjective follows "just" in this case (happiness is a noun); or alternatively: Everything was just dandy, until something happened...

We were at a very high point when this happened, so m. My family and I were gocoming downback down from the mountain fromusing stairs that awere up there, but mey kiddo decided to gocome down by jumping each step, t. The result iwas very obvious.

going is used when you are moving away from something (in this case the ground), but you want to come back down to the ground

I slipped down in the nexton the second to the last step, I rolled down and I almost fell out from the mountain.

or: fell off of the mountain
😳
Also, maybe you could explain how you slipped, to connect the previous sentence. (My kiddo bumped into me and I slipped...)

Beware your steeps...

"steep" situation, though

Once upon a time / A long time ago, my family and I went inton a mountain tour.

That mountain iwas around 200 meters at the toptall, but luckily we did not go too far.

As far I remember, the sightview (or "scenery") was very great and the nature peaceful.

We did normal things, as a normal family would do up there, we tooktaking some pictures, & selfies, and breathing fresh air (otherwise we would be dead hehe).

Everything was just happinessy, until something happened...

We were at a very high point when this happened, so: my family and I were going down the mountain fromusing the stairs that awere up there, but meI, a kiddo, decided to go down by jumping each step, and the result is/was very obvious.

I slipped down in the next -to the -last step, I rolled down and I almost fell out fromff (or "down) the mountain.

the next-to-last step
off (or down) the mountain

BewareWatch your steepsp...

nNear-dDeath eExperience

Once upon a timeA while ago, my family and I went into a mountain tour.

There's nothing wrong, but "once upon a time" makes it sound like a fairytale, so I replaced it with "a while ago."

That mountain iwas around 200 meters at the toptall, but luckily we did not go too far.

As I remember, the sight wasbeing very great and the nature peaceful.

We did normal things, as a normal family would do up there, wNothing was out of the ordinary. We took some pictures, selfies, breathand took in some fresh air (otherwise we would be dead hehe).

Everything was just happiness,y until something (terrible) happened...

We were atFrom a very high point wheon this happened, soe mountain, me and my family and I were going down the mountain from stairs that are up there, but me kiddousing the stairs there, but, being the kid that I was, I decided to go down by jumping each step, the resul. What happens next is very obvious.

I slipped down ion the next to the last step, I rolled down and I almost fell out fromff the mountain.

BewareWatch your steepsp...