\documentclass{standalone}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
  axis equal, 
  xtick distance=1,
  ytick distance=1,
  tick label style={font=\scriptsize},
  scatter,
  only marks,
  point meta=explicit symbolic,
  scatter/classes={
    a={mark=*, gray},
    b={mark=pentagon*, gray},
    c={mark=diamond*, gray},
    d={mark=triangle*, gray}
  },
]
\addplot table[x=x, y=y, meta=k]{punkty.txt};
\end{axis}
\end{tikzpicture}

\end{document}