Urgent help as I have been hacked
A month ago i bought my little brother a laptop and it was registered using my emails. On 14th May he pirated a copy of resident evil and on the same day I had a login attempt made which the scammer deleted from my inbox so i did not see the notification. Yesterday I found a draft in my inbox sent from my account with a threat demanding money(bitcoin) in exchange for keeping my privacy (i am aware this part is a scam/not true). My issue is that the scammer has logged onto my outlook using a mobile device - i have tried resetting the password but it does not kick you out of the mobile app (not even me).
I have reset all my passwords - used sign out of all devices - reported it to authorities but no one can help me or believe me.
I know they are in there as they have been leaving scam phishing emails with threats for money.
Ive checked for rules to see if it was automated but nothing i see.
Please could I have some help on how to get rid of them -I have money tied up in the account and I cannot afford to delete it.