Can't Access my account

Hello,
I am grateful to have the opportunity of getting help from you.
If you please, can you help me with my yahoo mail logging in problem? I have an account, which I have been using for 13 years. Four days ago I could not log into it. I think someone stole it as the password, alternative e-mail, and phone no. had been changed. I could not reach the security questions as well. So I want a method to find the security questions option.
Thanks in advance for your help