After 3 weeks, I can say that my hair still doesn't have any issues with frizz! I used half the bottle even though I have long hair, which is a plus. It doesn't straighten because it's not a straightening treatment, for those who are confused, it just softens. The texture won't be pleasing after the first wash, it's sticky, but it's not a problem on the second wash. It doesn't provide the same hydration as a treatment at the salon, but the price-performance ratio is very good, I would buy it again.

For the first time, it yielded mediocre results. For about a week, my hair was indeed straight, but it became frizzy again. The frizz never went away. I didn't see a crazy and huge difference. Also, during blow-drying with the hairdryer, the smell was strong. It requires attention when drying it and takes a while to absorb. There is still plenty of product left, and I will definitely give it a second chance, but applying it with a brush.

It did exactly what it promises. Awesome, I highly recommend it for a light keratin treatment without the use of a straightener, only with the hairdryer. Very good ingredients, nice smell, no fumes. It made my hair straighter and shinier than ever, and they truly shine, I have never seen them so glossy...
I should mention that I already have straight hair but I just wanted them completely sleek, without any frizz. It achieved that, they look healthy, it gave them volume, I don't know how but it also reduced the oiliness, I believe.
However, this treatment is not suitable for very curly hair. It will not straighten them.
Edit:
It lasted even longer than expected. It's incredibly worth it.
My hair is shinier than ever, easy to comb, exactly as I wanted.
What's essential for me is that it works only with the hairdryer, because I'm afraid of damaging my hair with the straightener..