This example is fine, but there is a small problem: I can't place the table where I want to. For example
\documentclass{article}
\usepackage{makecell}
\setcellgapes{5pt}
\begin{document}
This text should be above
\begin{table}[]
\centering
\caption{Gruppo 6}
\label{my-label}
\makegapedcells
\begin{tabular}{ | >{\centering}p{2.75cm} | *{3}{>{\centering\arraybackslash}p{1.75cm} |}}
\hline\hline
\textbf{Title / Title} & \textbf{X} & \textbf{Y} & \textbf{Z} \\ \hline\hline
\textbf{A} & a\% & b\% & c\% \\ \hline
\textbf{B} & d\% & e\% & f\% \\ \hline
\textbf{C} & g\% & h\% & i\% \\ \hline
\textbf{D} & j\% & k\% & l\% \\ \hline
\end{tabular}
\end{table}
\end{document}

[h]. – Apr 08 '19 at 17:00