To forward your Gmail to Outlook 365, follow the steps given:
Install the Gmail Backup tool on your system and run it.
Choose Gmail(Backup Mails Only). Sign in with your Gmail credentials.
Select Gmail mailboxes > Next > Migrate in Email Client.
Further, select Office 365 as the email saving format.
Sign in to your MS Office 365 account > Next.
Apply optional filters and additional features. Click Next.
Select the folder to transfer your Gmail mailbox, and click Next.
Lastly, hit Download.