The drop in site rank

Advert test

I'm not involved with website designing. My job is related to designing and manufacturing of various advertising boards. These days, the competition in this field has increased, and in order to outsmart competitors, I decided to launch a site for a long time, starting with a site design company. I was a good site for a while, but for the time being, my site's rating was good, but now, despite the fact that they are doing site optimization, they found a site and keywords dropping a lot that I asked the company, saying that due to Google's algorithms, this drop has been ranked. The same problem causes this problem or it can lead to other problems Of
Please give me some guidance