Some changes can be seen very quickly, and these are usually the changes made on the site (ON Site optimization). Regarding the changes in positioning, they start to appear after the first 3-4 months, but they are not always final and can fluctuate a lot (eg: one day the site is on page 2, and the next day it jumps on the page 10), this is due to the fact that google robots are constantly indexing new information about the site. According to Google, depending on the age of the domain, the articles posted may take between 8 and 38 weeks to be fully indexed; therefore, even after the 6-month optimization period, there is still a period of at least 3-4 months until the final results are seen.