How can I change the font in latex Beamer (using LuaLatex) to Calibri font?

Question

When trying to reproduce a slide in Powerpoint (with font Calibri) to Latex beamer, I've noticed that the font used by Latex beamer "takes more space": it uses a larger space between words and the letters also look like wider. Here is the Powerpoint output:

And here is the latex beamer output (the text in the third box needs two lines here, at the font takes more space):

I tried to change the font in latex to Calibri in order to use a font that takes less horizontal space (see my code below, the theme used can be found here), compiling it with LuaLatex (as recommended here), but it does not seem to change anything in the output. What am I doing wrong?

\documentclass{beamer}
\usetheme{theme1}
% packages
\usepackage{graphicx}
\usepackage{hyperref} % allows clickable urls
\usepackage{tikz}
\usepackage{listings} % show code
\usepackage{fontspec}
\setmainfont{Calibri}
\usepackage{tikz}
\usetikzlibrary{snakes}
\usetikzlibrary{positioning}
\newlength\yearposx
\makeatletter
\def\blfootnote{\gdef@thefnmark{}@footnotetext}
\makeatother
\definecolor{lightgrey}{RGB}{245,245,245}
% slide numbering
\setbeamertemplate{sidebar right}{}
\setbeamertemplate{footline}{%
    \hfill\usebeamertemplate***{navigation symbols}
    \hspace{1cm}\insertframenumber{}/\inserttotalframenumber}
% define title page
% begin document
\begin{document}
\frame{
    \frametitle{a}
    %till 2000
\begin{center}
  \makebox[0pt]{%

\scalebox{0.7}{%
\begin{tikzpicture}[
node distance=1.5 cm and 0.8cm,
ar/.style={->,>=latex,thick},
mynode/.style={
  draw,
  line width=1pt,
  text width=3cm,
  minimum height= 1 cm,
  align=center
  }
]
\node[mynode,text width=3cm, fill=lightgrey] (c1) at (0,0) {Diagnosed};
\node[mynode,text width=3.5cm, fill=lightgrey, below=1cm of c1] (c2) {First-line regimen \[1cm]$  $};
\node[mynode,text width=3.5cm, fill=lightgrey, below=1cm of c2] (c3) {AAAA + AABB (CCCC) \[1cm]$  $};
\node[align=center,text width=3cm,left=2cm of c2] (c2_3) {First-line \ blbla};
\node[align=center,text width=3cm,left=2cm of c3] (c3_3) {Second-line \ blbla};
\node[draw,align=center,text width=18cm,below left =1cm and -11cm of c3] (text1) {\textbf{aaa}: Very long long long text 1 \hspace{0.5cm}
\textbf{aaa}: Very long long long text 2\hspace{0.5cm}
\textbf{aaa}: Very long long long text 3};
\draw[->,thick] (c1) -- (c2);
\draw[->,thick] (c2) -- (c3);
\end{tikzpicture}}}
\end{center}
}
\end{document}