If you delete all posts from your account, your activity and rank will definitely go down. Your credit will be in your account. But I think this is a very imaginative post even though it seems very simple to everyone. Maybe we all can answer simply but we are going through a lot of thinking whenever we go to express it. If you have decided to delete the post from your decision then I would say don't delete the post. From now on keep up the good quality posts. Do not delete all at once but gradually delete later.