Can you guys help me doing those things like the one that is signed/encircled in the picture below?
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
[scale=30,line cap=round,line join=round,x=0.06cm,y=0.03cm]
%\draw[mygreen!20, fill = mygreen!20] (0,0.5)--(0,1.375)--(4.2,0.325)--(4.0,-0.5)--(2,0)--cycle;
\draw[very thick, ->, >=stealth] (-0,0) -- (4.5,0) node[anchor=north] {Tempo};
\draw[very thick,->, >=stealth] (0,0) -- (0,4.5) node[anchor=east] {Nível de Inventário};
\draw[very thick, domain=0:1.5, black!70, opacity=0.9, samples=200] plot (\x,{(-3*\x+3)});
\draw [very thick, black!70, samples=200, dashed] (1.5,-3/2) -- (1.5,3);
\draw[very thick, domain=1.5:3, black!70, opacity=0.9, samples=200] plot (\x,{(-3*\x+7.5)});
\draw [very thick, black!70, samples=200, dashed] (3,-3/2) -- (3,3);
\end{tikzpicture}
\end{document}