Check these links for some instant advice and assistance...
https://www.consumer.ftc.gov/articles/how-recover-your-hacked-email-or-social-media-account
https://www.kaspersky.com/resource-center/threats/what-to-do-if-your-email-account-has-been-hacked
https://support.google.com/accounts/answer/6294825?hl=en
https://www.csoonline.com/article/3617849/15-signs-youve-been-hacked-and-how-to-fight-back.html