Is it normal for a 6 years old child to snore?

Common. The tonsils & adenoids in kids grow faster in early & middle childhood than other body parts.At 6-9 kids often snore.At this point the glandular tissue stabalizes its size but the kids continue to grow. By the mid teens the snoring has gone & relative tonsil size seems smaller, though they don't actually shrink. Snoring associated with excessive day sleeping may be a sign of sleep apnea. Ck it out.
No. Talk with your child's doctor, your child may need their tonsils and / or adenoids removed.
Common, but. 10-12% of children snore regularly. This does not mean it is "normal" or without consequence. It can be due to uri, stuffy nose, allergy or obstructive sleep apnea. Snoring combined with any of gasping, snorting, waking up at night , bedwetting, restless sleep, overtiredness, crankiness or hyperactive behaviors is especially concerning and should trigger evaluation and a sleep study.