documentclass[12pt]{scrreprt}
usepackage[a4paper, includehead, left=3.5cm, right=1.7cm, top=2.5cm, bottom=2.0cm]{geometry}

usepackage[no-math]{fontspec}
setmainfont{Arial}



usepackage[ngerman]{babel}
usepackage{array,booktabs,amsmath}

usepackage[]{siunitx}
sisetup{load-configurations = abbreviations}
sisetup{locale = DE,group-separator={.}}
sisetup{per-mode=symbol}
sisetup{detect-all}

begin{document}



begin{align*}
 t_a  & =  frac{v}{a} & h_a & =  frac{1}{2} times a times {t_a}^2 \
h_v & =  h_t - h_a - h_r & t_v & =  frac{h_v}{v} \
t_t & =  2 times (t_a + t_v + t_r + t_d) & &
intertext{Some Text}
t_a & = frac{SI{6}{metrepersecond}}{SI{0,6}{metrepersecondsquared}} & h_a & = frac{1}{2} times SI{6}{metrepersecondsquared} times {SI{10}{s}}² \
& = SI{10}{s} & & = SI{30}{m} \[1ex]
t_v & = frac{SI{240}{m}}{SI{6}{metrepersecond}} & h_v & = SI{300}{m} - SI{30}{m} - SI{30}{m} \
& = SI{40}{s} & & = SI{240}{m} \[1ex]
t_t & = 2 times (SI{10}{s} + SI{40}{s} + SI{8}{s} + SI{120}{s}) \
& = SI{356}{s}
end{align*}


end{document}