\documentclass{standalone}
\usepackage[polish]{babel}
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,intersections}

\begin{document}

\begin{tikzpicture}
\draw[thick,->] (0,0) -- (5.5,0);
\draw[thick,->] (0,0) -- (0,4);
\draw[name path=l1] (0,0) .. controls (1,5) and (2,3.5) .. (5,0.5);
\draw[name path=l2] (0.5,3.5) .. controls (1,1) and (3,0) .. (5,3);
\draw[name intersections={of=l1 and l2, name=i}] (i-1) -- (i-2);
\draw[fill=gray] (i-1) circle (2pt);
\draw[fill=gray] (i-2) circle (2pt);
\end{tikzpicture}

\end{document}