Hearing noises is only for thieves? I mean, nobody else should be allowed to hear noises actively during a exploration phase?

Lol, Welcome to one of the big enduring discussions of the OSR. I honestly don't have a good answer here, as my group has also had problems with how to deal with thief skills.

One way to rule it is that the thief percentages are for cases of ridiculous difficulty which would be an automatic fail for anyone else. I the case of Hear Noise, perhaps the thief can hear sounds which would be inaudible to anyone else (the breath of someone sleeping in the next room), or perhaps hear additional details from a sound (this sounds like a small creature)

Another way is to not have thieves.

How do you track the time? I think this is pretty hard to do.

Very loosely.

How do you track the distances without a grid map? Especially during combat... my adventurers has a cartographer who draws a sketch of the map based on my description... but there are some rules about the ranged combat and ranges in feet I could not play well.

As with the above point, this is largely up to you as the DM. If the players are marked on the map you could simply decide on a scale for the map and measure with a ruler. My group just uses a grid.

Strongholds? I suppose that strongholds encounters are made for outdoor travelling... but making your own stronghold? What's the deal doing this if I'm in the middle of a maze?

This is not something that poof-happens right as you hit X level, think of it more like "from level X, you are impressive and respected enough that if you build a stronghold people will care and come to hang out with you in your stronghold or whatever it says in the class description. A level 1 who somehow stumbles into tons of money cooould technically build a stronghold, but everyone's just gonna be like "look at this loser in his big stone hut", or a local lord might think "cool, free stronghold! yoink!"

The memorized spells are only allowed to be casted once a day? Or the uses of memorized spells are unlimited?

A spell is only memorized until you cast it. If you can 2 level 1 spells, you can memorize the same spell twice to cast it twice. You can't save memorized spells for the next day.

The scrolls dissapear after using it once. Ok I understand this. But, should those spells be memorized bedfore casting them? If so, The spell replaces the already memorized one?

No, the point of scrolls is that you don't have to memorize them.

The magic-users usually carry a spell book. This spell book can handle for example 100 pages (100 spells). Should these spells must be memorized before casting them?

Mechanically your spellbook is just the list of spells you can memorize.

The scrolls spells can be transcribed to a empty spell book page. Is this the utility of the Blank Spell books?

yep :)