Hi, can you give me advice which Minor scale i have to start first. I know there are 3 kinds of minor scales: natural, harmonic and melodic. I have already finished major scales, so i have to start with minors, but i dont know which one to choose.
Thanks in advance.

Harmonic is the one used in most western music you will encounter, and the most important to be familiar with.

My teacher started me with the natural minor. Then taught the melodic and harmonic as variations on the natural. The melodic has a raised 6th and 7th when ascending and is the same as the natural when descending. The harmonic has a raised 7th in both directions.

I'll ditto what bluekeys had to say. Natural minor is The Minor Scale, Aeolian if you like. For what it is worth I learned the natural minor scale -- it gave me what I needed and I never ventured beyond that, unless you count parallel modes using Dorian and Phrygian as venturing further.