Sorry but this sounds like "now draw the rest of the owl" to me... How do you find leads? How do you market products to them? How do you get them to say a word of feedback? How do you close the deal? How do you retain the customer?

I am trying hard for the past decade but all of these still go right around my head.

> I am trying hard for the past decade but all of these still go right around my head.

What have you tried so far? There is plenty of information available (even in these comments) about how to find customers.