You can merge multiple Google accounts into one, but there's no fully automated way to do it. You'll need to manually transfer your data out of and into every individual Google app you use, such as Gmail, Google Calendar, and Google Drive. However, you can forward new emails from your old account to your new one using email forwarding in Gmail. To set up email forwarding, log in to your old Gmail account, click on the Settings icon, select See all settings, then Forwarding and POP/IMAP, Add a forwarding address, enter your new email address, and confirm. You can also send emails from your old Gmail account by adding it as an "Add another email address" in the Send mail as section of your Gmail settings. To back up and move your old Gmail emails, you can use Gmail's import feature or Google Takeout to export your emails as a CSV file. Once exported, you'll need to import the archive into your new Gmail account using an email app like Apple Mail or Microsoft Outlook. Additionally, you'll need to manually merge your Google Contacts and Google Calendar accounts by exporting them from your old account and importing them into your new one.