\documentclass[10pt,a4paper]{article}
\usepackage[margin=2cm]{geometry}
\usepackage{utopia}
\usepackage{lipsum}
\usepackage[dvipsnames,svgnames]{xcolor}
\definecolor{bistre}{RGB}{61, 43, 31}
\definecolor{bistreb}{RGB}{150, 113, 23}
\definecolor{bistref}{RGB}{133, 109, 77}
\definecolor{bistres}{RGB}{128, 117, 90}
\definecolor{stempel}{RGB}{0 34 85}
\definecolor{biruku}{cmyk}{1,0.80,0.30,0.05}
\definecolor{myblue1}{RGB}{0,82,155}
\definecolor{myblue}{RGB}{40,96,139}
\definecolor{blau}{RGB}{17,94,140}
\definecolor{paper}{RGB}{239,227,157}
\definecolor{rusia}{RGB}{85 85 57}
\definecolor{coklat}{rgb}{.6,0,0}
\definecolor{anggur}{rgb}{0.5,0,0}
\definecolor{ocre}{RGB}{243,102,25}
\definecolor{birugelap}{rgb}{.11,.23,.60}
\usepackage{tcolorbox}
\tcbuselibrary{skins, breakable}
\tcbset{examplebox/.style={enhanced,colback=white,colframe=white,
enlarge top by=10mm,
overlay={%
\path[fill=birugelap,line width=.4mm] (frame.north west)--++(17mm,0)coordinate(n2)--++(0,8mm)--++(-20mm,0) arc (-90:90:-4mm)--cycle;
\node at ([shift={(5mm,4mm)}]frame.north west){\color{white}{\textbf{\sffamily Theoreme}}};
\path[fill=JungleGreen] ([xshift=.4mm]n2)--++(0,8mm)--++(7mm,0)--++(0,-8mm)--cycle;
\node at ([shift={(4mm,4mm)}]n2){\color{white}{\textbf{\sffamily \themycounter}}};
\node at ([shift={(18mm,4mm)}]n2){\textbf{Ouzin}};
}}}
\newcounter{mycounter}
\begin{document}
Some text before ...
\begin{tcolorbox}[examplebox,step=mycounter,label=one, breakable=unlimited]
This is a \textbf{tcolorbox}.\par
a lot of text here ... This is Example \ref{one}
\lipsum[1-7]
\lipsum[1-9]
\end{tcolorbox}
\begin{tcolorbox}[examplebox,step=mycounter,label=two, breakable=true]
This is a \textbf{tcolorbox}.\par
a lot of text here ... This is Example \ref{two}
\lipsum[1-6]
\lipsum[1-7]
\lipsum[1-9]
\end{tcolorbox}
Some text after ...
\end{document}
