For many years, Google has provided a custom search facility that can be built to search the content of a website. Knowing the pages within your website it would display the relevant results for a search phrase within each website.
Google would display its own paid advertisements at the top of these search results. This obviously encourages the visitor to click on one of these advertisements, which takes them away from your website.
To prevent these adverts from being displayed, Google used to give you the option of hiding these advertisements in return for an annual payment. Google has now removed this option, so there is now no way of preventing these advertisements from appearing.
Your solution, get your web developer to replace this Google search facility with one of our own.