I handed my bitcointalk account to my friend few years ago and he started doing paid shit posting. Now I asked him to provide me the account login and when I checked that its simple got down voted.
Yes (theymos) account is mine. I let my friend use that account. Now that he is the admin of the forum he is not returning the account to me
(I made a drama like yours 
)Is there anyway to fix my account reputation?
first of all There is no clear evidence that the account was used by your friend. And even if it did, it's entirely up to you and It's your fault. Because it is your responsibility to protect your account. So you have to take your account responsibility. I don't think the reputation of your account will be back again