As suggested by SamCarter...

\documentclass{article}
\usepackage{tikz}%,pgf}
%\usepackage{pgfplots}
%\usetikzlibrary{calc,angles}
\usetikzlibrary{angles}
%\usetikzlibrary{arrows}
%\usetikzlibrary{calendar}
%\usetikzlibrary{through}
%\usetikzlibrary{intersections}
%\usetikzlibrary{shapes,decorations}
%\usetikzlibrary{decorations.pathmorphing}
%\usetikzlibrary{decorations.pathreplacing}
%\usetikzlibrary{decorations.shapes}
%\usetikzlibrary{decorations.markings}
%\usetikzlibrary{decorations.text}
%\usetikzlibrary{positioning,automata,shadows}
%\usetikzlibrary{patterns}
\usetikzlibrary{quotes,arrows.meta}
%\usetikzlibrary{shapes.symbols}

\usepackage{fontawesome5}

\begin{document}

\begin{tikzpicture}
    % Draw the horizontal line
    \draw[dashed] (-1.5, 0) -- (9, 0);

    % Draw the slopes
    \draw[thick] (0, 0) -- (2.5,1.25);
    \draw[thick] (5.5, 1.25) -- (7.5,0);

    % Draw the vertical dashed lines
    \draw[dashed] (2.5, 0) -- (2.5,1.25);
    \draw[dashed] (5.5, 0) -- (5.5,1.25);

    % Labels for points
    \node at (0, -0.2) {A};
    \node at (2.5, 1.5) {B};
    \node at (2.5, -0.3) {I};
    \node at (5.5, 1.5) {C};
    \node at (5.5, -0.3) {J};
    \node at (7.5, -0.3) {D};

    % Vectors
    \draw[->] (2.5,0) -- (3,0) node[below] {$\overrightarrow{i}$};
    \draw[->] (2.5,0) -- (2.5,0.5) node[left] {$\overrightarrow{j}$};

    % Angle
    \coordinate[label=below:] (A) at (2.5,1.25);
    \coordinate[label=above right:] (B) at (0,0);
    \coordinate[label=above right:] (C) at (2.5,0);
    \draw pic [draw,-,"$\alpha$",angle radius=12pt,angle eccentricity=1.5] {angle = C--B--A};

    \path (A) -- (B) node[midway, sloped, above, inner sep=0pt] {\Large\faSkiingNordic};

\end{tikzpicture}

\end{document}

is it possible to reproduce this schema with tikzpicture ?

Yes, as you've seen already. Here is a way to do it via my SVG suggestion C)

Now, this one is simple, as it has been asked and answered before specifically for a skier, AND exhaustively for SVG to Tikz, see e.g. herein.

(For sake of completeness and for not getting lost inside comments I put this as a separate solution approach.)

is it possible to reproduce this schema with tikzpicture ?

Yes, as you've seen already. Here is a way to do it via my answer in comment A)

1. Get an image

So I found an uphill skier on a sign. Cur it out, filled white with black, deleted background to make it transparent. Saved as skierimg.png :

BTW, it's no big deal to redraw such a line art with some drawing tool or TikZ.

2. Adjusting your code

• using package graphicx
• calling the image inside a \node
• and yes, you could rotate it a few degrees via node or includeimage ...

\documentclass[10pt,border=3mm,tikz]{standalone}
\usepackage{graphicx}


    %%\documentclass{article}
\usepackage{tikz}%,pgf}
%\usepackage{pgfplots}
%\usetikzlibrary{calc,angles}
\usetikzlibrary{angles}
%\usetikzlibrary{arrows}
%\usetikzlibrary{calendar}
%\usetikzlibrary{through}
%\usetikzlibrary{intersections}
%\usetikzlibrary{shapes,decorations}
%\usetikzlibrary{decorations.pathmorphing}
%\usetikzlibrary{decorations.pathreplacing}
%\usetikzlibrary{decorations.shapes}
%\usetikzlibrary{decorations.markings}
%\usetikzlibrary{decorations.text}
%\usetikzlibrary{positioning,automata,shadows}
%\usetikzlibrary{patterns}
\usetikzlibrary{quotes,arrows.meta}
%\usetikzlibrary{shapes.symbols}

\begin{document}

\begin{tikzpicture}
    % Draw the horizontal line
    \draw[dashed] (-1.5, 0) -- (9, 0);

    % Draw the slopes
    \draw[thick] (0, 0) -- (2.5,1.25);
    \draw[thick] (5.5, 1.25) -- (7.5,0);

    % Draw the vertical dashed lines
    \draw[dashed] (2.5, 0) -- (2.5,1.25);
    \draw[dashed] (5.5, 0) -- (5.5,1.25);

    % Labels for points
    \node at (0, -0.2) {A};
    \node at (2.5, 1.5) {B};
    \node at (2.5, -0.3) {I};
    \node at (5.5, 1.5) {C};
    \node at (5.5, -0.3) {J};
    \node at (7.5, -0.3) {D};

    % Vectors
    \draw[->] (2.5,0) -- (3,0) node[below] {$\overrightarrow{i}$};
    \draw[->] (2.5,0) -- (2.5,0.5) node[left] {$\overrightarrow{j}$};

    % Angle
    \coordinate[label=below:] (A) at (2.5,1.25);
    \coordinate[label=above right:] (B) at (0,0);
    \coordinate[label=above right:] (C) at (2.5,0);
    \draw pic [draw,-,"$\alpha$",angle radius=12pt,angle eccentricity=1.5] {angle = C--B--A};

    % Skier on the slope
%    \draw[thick] (1.25, 0.625) circle (0.15); % Head
%    \draw[thick] (1.25, 0.625) -- (1.25, 0.1); % Body
%    \draw[thick] (1.25, 0.4) -- (1.1, 0.3); % Left arm
%    \draw[thick] (1.25, 0.4) -- (1.4, 0.3); % Right arm
%    \draw[thick] (1.25, 0.1) -- (1.1, 0); % Left leg
%    \draw[thick] (1.25, 0.1) -- (1.4, 0); % Right leg

    \node at (1,.9) {\includegraphics[width=1cm]{skierimg.png}};

\end{tikzpicture}

\end{document}

is it possible to reproduce this schema with tikzpicture ?

Yes, as you've seen already. Here is a way to do it via my scribble suggestion B)

1. Scribble the skier uphill

I did what I wrote: sketched it with pen on paper. Though I could have scanned it, I just recreated it as a bitmap, with focus on upslope and relevant posture, and with mouse jitter, without smoothing:

2. Converting it to TikZ

It's a bit tricky, as pixel coordinates increase to the right AND downwards, while TikZ uses mathematical conventions (to the right AND upwards). To simplify my work I:

• mirrored the image at the horizon (so it's upside down)
• read pixel coordinates with the mouse cursor (e.g. 109/227px) and simply divided by 100 (1.1/2.3cm) for TikZ

Now you have a tikzle as a kind of line art ...

• to reuse certain coordinates I put (A) and (C) for hip and head
• and a variable shoulder coordinate at (B)

\documentclass[10pt,border=3mm,tikz]{standalone}


\begin{document}
 % ~~~ sketch copy: inverted bmp, px/100 ~~~~~~~
 \begin{tikzpicture}[
    sh/.style={pos=.7,inner sep=0},
    hd/.style={draw,fill=black,circle,
               inner sep=0,minimum size=1mm},
 ]
    % ~~~ skies ~~~~~~~
    \draw (  0,  0) -- (2.3,1.3);
    \draw (0.5,0.5) -- (2.3,1.9);
 
    % ~~~ feet + legs ~~~
    \draw (1.3,0.9) -- (1.1,0.8) -- 
          (1.3,1.4) -- (1.3, 1.9) coordinate(A);
    \draw (1.7,1.5) -- (1.4,1.3) -- (A);
 
    % ~~~ spine ~~~~~~~~
    \draw (A) -- node[sh] (B) {} (2,2.8) coordinate (C);
    
    % ~~~ arms+sticks ~~~~
    \draw (B) -- (3.2,2.5) -- (2.6,1.1);
    \draw (B) -- (2.8,2.7) -- (2.1,2);
    
    % ~~~ head ~~~~~~~
    \node[hd] at (C) {}; 
 \end{tikzpicture}
\end{document}

3. Where to go from here?

Many options. E.g. you could:

• put the code inside a \pic, so you can place myrades of skiers
• parametrize it more, e.g. assign each absolute coordinate to \coordinate, so you can manipulate it easier
• impact on line widths, perhaps even schange its line style with decorate or so (though that's more limited than from using brushes in raster-drawings)
• introduce caps or tips at line ends
• turn straight lines into bends, e.g. by replacing some -- with to[out=,in=]
• ... the sky's the limit, not the skier ;-)

EXAMPLE:

    % ~~~ spine ~~~~~~~~
    \draw (A) to[out=70,in=190] node[sh] (B) {} (2,2.8) coordinate (C);
    
    % ~~~ arms+sticks ~~~~
    \draw (B) to[out=2,in=130] (3.2,2.5) -- (2.6,1.1);
    \draw (B) to[out=2,in=130] (2.8,2.7) -- (2.1,2);