I understand you're using the HubSpot Sales Chrome extension with Gmail and that contacts get created in HubSpot when you send emails from Gmail, correct?
To avoid that, you should make sure that you do not log the emails when you send them. For that you can either customize your default parameters so that no emails get logged into HubSpot except if you're specifically asking the extension to, or you can uncheck the log button when you draft the email. That way these contacts will not be created in HubSpot.
Would you mind clarifying what do you mean by gmail integration? Can you send me screenshots of what you're talking about?
From what you're explaining, I'm wondering if maybe you did connect your email address as a team inbox in HubSpot. In that case, every incoming email will arrive in Conversations > Inbox. This is expected behaviour. If you do not want that you will need to disconnect this inbox as a team inbox and then connect it again as a personal inbox. You have more information regarding these two connections here.