I've attached a basic GarageBand course [click More Info in the graphic at the top] -- that should provide a lot of answers. - I wouldn't use iCloud unless you're collaborating with someone -- it's easy to lose track of dependent audio files - Correct, recording voice or any real [physical] instrument will create [large] audio files [7.5MB/min/track]; recording on a Software Instrument track will not [adding only a tiny bit to the size of the Project itself] - With GB a Project is usually a particular song - 24-bit recordings have wider dynamic range and low-level audio is cleaner [subtly better sound quality] -- it's the standard nowadays

You write that at 24-bit resolution audiofiles will take up 7, 5mb per minute per mono track. Why mono? I need all my sound will be in stereo. I already have 24-bits selected there by default, but i already have selected export projects at full volume by default, but on the screenshot you haven't selected the last one, why? Is that bad will be selected export projects at full volume or what for it good?

It's just a reference measurement for file size -- if you record in stereo your stereo [2-channel] audiofiles will simply be twice as big per minute. The "full volume" option may change the level of the finished recording -- professional engineers/mixers don't use it because they need to control the overall level of finished recordings manually [especially for streaming services] but it's up to you if you want it on or off.

But if I want a real song, all real songs on the radio, cd's, on the concerts - they are all in stereo. Where is the sense to record in mono (only smaller file size), if the quality song is in stereo? Do the gb records projects in stereo by default? Do you record your song in mono or in stereo? I have downloaded a dictaphone and changed stereo to mono and choosed mp3, but still the file size is the same (by memory) like in QTP or like it was in stereo in dictaphone. Why? You wrote that the size of mono and stereo is twice.

I watched video above and there were midi track, audio track, and drummer. I didn't understood last one. If I hit +, get drummer (last choice), does it work without external audio instrument? Is it anything on its own, or does it is related to audio options?

I don't understand, why you wouldn't use Icloud. You wrote it's easy to lose a track of dependent audio files. What that's mean? That a file in Icloud will disappear itself to nowhere.. ? What means lose a track? Track is a song/project, or what? I want to keep my projects in Icloud, because I know there can be an error of hard disk and all my saved work then certainly WILL disappear to nowhere - I don't want that kind of trouble to myself. Cloud storage should be a safe in case of "death" of Mac. Isn't so?

If you prefer to use iCloud for storage then by all means go ahead and use it -- I prefer to store my projects/audio/dependent files locally and maintain up-to-date backup[s].

Does gb records projects by default mono or stereo and what is a drummer (hitting plus), midi or audio track, or both?

Mono track takes 7, 5mb per minute. So stereo track takes 15 mb per minute. Is track an instrument? So, if I have 3 minutes song in stereo and 4 instuments (tracks?), it means 4x15mb (all 4 tracks per minute)=60mb, and 60mb x 3 (minutes) = 180 mb per 3 minute song in stereo with 4 instruments (tracks). Correct?

Yes, the math is exactly correct! But keep in mind that the 7.5MB/min/track applies only to Audio Tracks, not Software Instrument tracks, which record MIDI data instead of audio -- MIDI data takes up very very little memory.