It's pretty much impossible to give you any advice based on the info you provided...
What are you selling, are these cheap or expensive goods? Do you track "add to cart" events, if so, were there any? What does your store look like, is it fully functional, did you test properly?
I see 17, then 35 and then 800 clicks ... it's in Italian, I think, so don't understand it fully ... are these 3 different adsets or just different objective? The third one is getting you VERY cheap clicks, I guess it's very broad targeting maybe with some misleading or confusing/unrelated angle ... The other two "adsets" gave you only a bunch of clicks, so it's nothing unusual to not have a sale from so few clicks.
More info is definitely needed in order for anyone to help you identify the problem.