Modifying the headline shape in Beamer Warsaw in class beamer Warsaw

Question

I would like to use beamer: Create own headline theme to custom my headline theme but unfortunately my presentation started with table of content instead of titlepage and with zero

i would like my presentation to strat with titepage without counter number and the plan (table of content) start with zero after that

1. Section ( long text here I)
2. Section ( long text here II) and so on

\documentclass[hyperref={pdfpagemode=FullScreen,colorlinks=true},
xcolor={dvipsnames,svgnames,table}]{beamer}
\usepackage{concrete}
 \usetheme{Warsaw}
\setbeamercovered{transparent}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[english,french]{babel}
\usepackage{dsfont}
\usepackage{pifont}
\usepackage{enumitem}
\usepackage{pdfpages}% pour insérer des pages précises d’un pdf multipages
  \setlength\parindent{0pt}
\title[Very Very Long title here  ] %optional
{Very Very Long title here}
%\subtitle{A short story}

\author[Mohcine] % (optional, for multiple authors)
{Mohcine }

\institute[VFU] % (optional)
{
  Faculty of Mathematics\\
  Very Famous University

}

\date[VLC 2013] % (optional)
{Very Large Conference, March 2015}

%\logo{\includegraphics[height=1.5cm]{lion-logo.png}}
 \usepackage{color}
 \makeatletter
\def\colorizemath #1#2{%
    \expandafter\mathchardef\csname orig:math:#1\endcsname\mathcode`#1
    \mathcode`#1="8000
    \toks@\expandafter{\csname orig:math:#1\endcsname}%
    \begingroup
       \lccode`~=`#1
       \lowercase{%
    \endgroup
       \edef~{{\noexpand\color{#2}\the\toks@}}}%
   }
\@for\@tempa:=a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z\do{%
    \expandafter\colorizemath\@tempa{green}}
\@for\@tempa:=A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z\do{%
    \expandafter\colorizemath\@tempa{green}}
\@for\@tempa:=0,1,2,3,4,5,6,7,8,9\do{%
    \expandafter\colorizemath\@tempa{red}}
\makeatother

\everymath{\color{blue}}
\everydisplay{\color{blue}}



\definecolor{secinhead}{RGB}{249,196,95}
\definecolor{titlebg}{RGB}{51,51,51}

\setbeamercolor{secsubsec}{fg=secinhead,bg=black}
\setbeamercolor{frametitle}{fg=secinhead,bg=titlebg}

\usepackage{tikz}
\usetikzlibrary{shadings}
\definecolor{secinhead}{RGB}{249,196,95}
\definecolor{shadowbg}{RGB}{51,51,51}

\setbeamercolor{secsubsec}{fg=secinhead,bg=black}
\setbeamercolor{shadow}{fg=secinhead,bg=shadowbg}

\setbeamertemplate{headline}
{
  \leavevmode%
  \hbox{%
  \begin{beamercolorbox}[wd=\paperwidth,ht=8.25ex,dp=3.5ex]{secsubsec}%
    \raggedright
    \hspace*{2em}%
    {\sffamily\Large\color{secinhead}\thesection.~\insertsection\hfill\insertsubsection}%
    \hspace*{2em}%
  \end{beamercolorbox}%
  }\vskip-1pt%
  \hbox{%
  \tikz\draw[draw=none,top color=black,bottom color=shadowbg!60] (0,0) rectangle (\paperwidth,0.5);
  }%
}

\begin{document}
\setbeamertemplate{navigation symbols}{}

 \AtBeginSection[]

{
  \begin{frame}
    \frametitle{Table of Contents}
    \tableofcontents[currentsection]

  \end{frame}
}

\frame{\titlepage}

\section[Plan]{}
\begin{frame}[allowframebreaks]
\tableofcontents
\end{frame}

\begin{frame}
\frametitle{Table of Contents}
\tableofcontents
\end{frame}

\section[long text here I]{long text here I}
\begin{frame}
\end{frame}

\section[long text here II]{long text here II}
\begin{frame}
\end{frame}
\section[long text here III]{long text here III}
\begin{frame}
\end{frame}
\end{document}

Answer 1

The document starts with

 \AtBeginSection[]

 {
     \begin{frame}
     \frametitle{Table of Contents}
     \tableofcontents[currentsection]

     \end{frame}
}

and because \AtBeginSection is separated (empty line) from {\begin{frame}... this frame is considered part of your presentation and not what should be done before every section starts. If this empty line is deleted or commented out,

 \AtBeginSection[]
 {
     \begin{frame}
     \frametitle{Table of Contents}
     \tableofcontents[currentsection]

     \end{frame}
}

or

 \AtBeginSection[]
 %    
 {
     \begin{frame}
     \frametitle{Table of Contents}
     \tableofcontents[currentsection]

     \end{frame}
}

everything will work. Although I'd suggest to move \AtBeginSection to the preamble.