Can an SEO specialist wind up traffic from bots to my site to show the result?

Question

Search Engine Optimization

I have a situation: I found an SEO master on the ad so that he would start promoting the site, he looked and said that he would increase targeted traffic in a month by 2-3 times, then every month more and more. He also had to make optimizations. I transferred the money immediately 100%, he was silent for 3 weeks, did not answer calls. Traffic to the site did not change, it was the same - about 350 uniques per day.
A week ago, he wrote that he was in the hospital, but he was working on my site and traffic will start from that day. And from that day on, I noticed according to Yandex metrics that there were sharply 500 uniques, the next day 550, and until today, for a week already - 500 uniques on average.
The problem is that traffic has increased, but the conversion has fallen. The site sells household small things, and earlier there were 6-12 sales on average per day (from 300-350 uniques). In recent days, sales have become 2-4, less than before. How so if the traffic has increased? Not targeted traffic?
I went into the webvisor and saw the following picture: visitors come from Yandex for a high-frequency query (I didn’t even try to promote them) to the main page (I didn’t really promote it either, this is not a landing page), they are on the main page 5-30 seconds and exit. They don't go anywhere, not in any section.
Then I noticed such visitors - 30 seconds on the main page, 30 seconds on the "Contacts" page and exit. And there are a lot of such visitors.
I looked at the webvisor that was up to this week - there were no such visitors.
The feeling that the SEO has caught up with the bots to show that the work has been done.
Tell me if this is possible?

Answer 1

In general, it is possible that your site will fall under the ACS for incomprehensible behavioral factors.

Answer 2

not even a SEO specialist can wind it up

Answer 3

500 can easily, without straining, with ordinary proxies,
at least check the parameters of visitors (country, IP, etc.)
it’s not particularly dangerous, except for hosting costs

Answer 4

99% it's a cheat. I will leave 1% in doubt because. I did not see the statistics of the metric. By the way, for this you can fly to the ban for 9 months. Optimization is easy to check, ask for a plan of work performed. I doubt that they did something with the site))