Smooth hair permanently
I have natural curls and smooth my hair in a very simple way ... I take perm water.
It can also be used to straighten hair: do not wind, but apply and comb smoothly, and let it absorb just as long as a normal perm.
So: buy permanent water, apply and comb smooth, wash out, done.
The whole thing holds for me about the 3-4 months. Just do not use that often, as it is well known that permanent whitewash attacks your hair at some point.
But for smoothing permanently I can only recommend this method.