documentclass[a4paper,12pt,twoside]{article}
usepackage[top=2.5 cm, bottom=2.5 cm, left=4 cm, right=2.5 cm]{geometry}
usepackage[turkish,shorthands=:!]{babel}
usepackage{fontspec}
usepackage{titlesec}
setmainfont{Times New Roman}
usepackage{blindtext}
begin{document}
begin{titlepage}
This is title page
Blindtext
end{titlepage}
Blindtext
newpage
section*{abstract}
This must be aware of the effects of twoside code.

blindtext
newpage
end{document}