# 3 point draw a Parabola

\begin{tikzpicture}[scale=1.6]
\begin{axis}[
xmin=-0.02,xmax=0.12,
ymin=-2,ymax=15,legend style={nodes={scale=0.6, transform shape}},
legend image post style={mark=*}, xlabel=$Axialrichtung (mm)$,ylabel=$Spannung (MPa)$]

\draw[red] (axis cs: -0.02, 0) -- (axis cs: 0, 11.045);
\draw[red](axis cs: 0,11.045) parabola bend ( axis cs: 0.1,0) (axis cs: 0,-11.045) ;
\end{axis}
\end{tikzpicture}


It should be one parabola open to left, not two*0.5 parabolas open to up and down. Where am I wrong?

Welcome to this site! You need to rotate the parabola, the standard construction is only for "upright" parabolae. Please also provide complete codes. Further information can be found in the comments in the following (complete) code.

\documentclass[tikz,border=3mm]{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[scale=1.6,%<- put scale into the axis options
xmin=-0.02,xmax=0.12,
ymin=-2,ymax=15,legend style={nodes={scale=0.6, transform shape}},
legend image post style={mark=*}, xlabel={Axialrichtung (mm)},
ylabel={Spannung (MPa)}]%<- removed math mode
%others do not have your data files