how to write menor scales

Which minor scale? Depending on how you look at it, there are anywhere from three to ten (?) different minor scales. See https://en.wikipedia.org/wiki/Minor_scale.

The scales most commonly referred to as "minor" are the "natural minor scale", the "harmonic minor scale", and the "melodic minor scale".

The "natural minor scale" is also referred to as the "aeolian mode". It consists of the same notes as the relative major scale, but starting at the sixth degree of the major. For example, the A (natural) minor scale is the same notes as the C major scale, but starting at A. Thus, A, B, C, D, E, F, G, A.

The "harmonic minor scale" solves the problem of the "natural minor scale" not having a "leading tone" to the root. Take the "natural minor scale" and raise the seventh degree a half-tone: For example, the A (harmonic) minor scale is A, B, C, D, E, F, G#, A.

The "melodic minor scale" solves the problem of the "harmonic minor scale" having an augmented second interval from its sixth to seventh degrees. Since the sixth degree of the "harmonic minor" is a half-tone above the fifth, the "melodic minor scale" raises the sixth degree by a half-tone. But only when the scale is ascending! When descending, the "melodic minor scale" is identical to the "natural minor scale". For example, the A (melodic) minor scale is A, B, C, D, E, F#, G#, A, when ascending and is A, G, F, E, D, C, B, A, when descending.

Composers often use all three of these scales interchangeably when composing a minor melody.