My account merged with another account now I am not admin anymore.
They shared a link and I accepted but now I don't have controlled of my Dropbox.
It sounds like you were sent an invitation to join a Dropbox Business team. Accepting would merge your account into the business account, effectively making them the owner of your account. If you had your own paid subscription, you would have received a prorated refund back to your original payment method.
If you no longer wish to be a part of the Business team, you need to ask their team admin to convert your account back to a personal account. It's very important that the admin doesn't just remove you from the team as doing so would delete your account. If that were to happen, the team admin would only have seven days to restore your account for you. They need to convert your account. Once your account is converted back to an individual account, you can resubscribe if you had a paid subscription.