#1
Does the action and inntonation affect the sustain of my guitar? Because my G string has high action and bad inntonation and the sustain is very short(I can't fix my action because I don't have the right tools).

For ex. my 12th fret on G lasts about 1 second.
#2
Intonation has no bearing on sustain. Action does; the higher your action is, typically the longer notes will sustain.

That said, the G string often won't sustain a note for as long as the other strings, especially at the higher frets. It's held at different tension to the others which also leads it to suffer from tuning problems more often. Without sitting down tih your guitar and seeing it in person myself, I can't suggest much other than "yup, G strings suck".
Yes, I know everything. No, I can't play worth a damn.
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