This is a very valid question. The time will depend on several factors, such as your current ranking and the difficulty of your keywords, etc.
Here is an analogy: Imagine that you are starting to take tennis lessons, after one week you will hit some balls, and after a couple of months you will be able to play a small match. Later on, you will probably win some competitions. Regarding SEO is similar: after a few weeks you will see some great results, but it will get better and better with time.
We can guarantee that your website will rank much better in just a couple of weeks after we start to work on its SEO. Our digital marketing company in HK will improve your current ranking by 50% in the first two weeks. If, for example, your website is ranking 60 on Google right now, we will bring you to position 30 in two weeks.
Furthermore, Arcopix will not force you to sign any yearly contract.