Roman is correct, the API and any internal calls close the db connection automatically so no need to attempt to close it manually unless you have some standard C# code you're writing and not using the Kentico API.
The first query is getting a
generalselect query statement from the
cms_query table. Based on the query statement, the
generalselect query is non-existent in an out of the box version of Kentico so this has to be something created by you or your team and being called from within the API. The majority of those statements are dynamically built so the
generalselect could be a property from a webpart or from an API call in something you or your team coded. Many possibilities.
Unless they are locking up the database or returning lots of data unnecessarily, I'd not worry much about them.