.GroupBy(..., numbersGroup => numbersGroup.Key),
.OrderByDescending(supergroup => supergroup.Key)
.First()

int[] numbers1 = { 1, 2, 3, 3, 2, 4 };

// First in GroupBy(x => x) I group all numbers within the array (remove all duplicates too?), now my array looks like this [1,2,3,4].
int[] result = numbers1.GroupBy(x => x)
// In GroupBy(numbersGroup => numbersGroup.Count()) I collect all the different amount of occurrences withing the array, that would be 1 (1, 4) and 2 for (2, 4) so my array should look like this now [1, 2].
// Now this is where things get out of hand, what happens at the rest of it? I have tried for 4 hours now and can't figure it out. What exactly happens in numbersGroup => numbersGroup.Key? .OrderByDescending(supergroup => supergroup.Key)?
.GroupBy(numbersGroup => numbersGroup.Count(), numbersGroup => numbersGroup.Key)
.OrderByDescending(supergroup => supergroup.Key)
.First()
.ToArray();