\usepackage{titlesec}

\providecommand{\DUdocumentsubtitle}[1]{%
  %\begin{nthcolumn}{1}
  \color{black}
  \em
  \EBLigatures\selectfont
  \Large
  #1
  %\end{nthcolumn}
}

\makeatletter

\def\@maketitle{%
  \vspace*{1cm}
  \begin{nthcolumn*}{1}%
  \raggedright
  \textcolor{orange}{%
    \fontsize{1.2cm}{2cm}\CaviarDreamsFont\selectfont \@title
  }
  \end{nthcolumn*}
}
\makeatother


\newcommand{\periodafter}[1]{#1.}

% Titre de niveau 1
\titleformat{\section}
  {\CaviarDreamsFont\selectfont\large}
  {\thesection}
  {0em}
  {\periodafter}
  [\titleline{{\color{backsidecolor}\titlerule[1pt]}}]

% Titre de niveau 2
\titleformat{\subsection}
  {\large}
  {\thesubsection}
  {}
  {\textcolor{backsidecolor}}

% Titre de niveau 3
\titleformat{\subsubsection}
  {\bfseries\normalsize}
  {\thesubsubsection}
  {2em}
  {}
  {}