documentclass[a4paper]{article}
usepackage{geometry}
geometry{
    a4paper,
    total={210mm,297mm},
    left=30mm,
    top=30mm,
    right=30mm,
    bottom=30mm
}

usepackage[T1]{fontenc}
usepackage{lmodern}
usepackage{mathptmx}
usepackage[english]{babel}
usepackage{graphicx}
usepackage[colorinlistoftodos]{todonotes}
usepackage{kpfonts}
usepackage{amsmath,amsfonts,amssymb}
usepackage{tocloft}
usepackage{authblk}
usepackage{abstract}
usepackage{fontspec}
usepackage{titlesec}
usepackage{slantsc}
usepackage{bold-extra}

renewcommand{absnamepos}{flushleft}
setlength{absleftindent}{0pt}
setlength{absrightindent}{0pt}
renewcommand{abstractnamefont}{fontsize{13}{16}scshapeitshapebfseriesselectfontparskip6pt}
renewcommand{abstracttextfont}{fontsize{10}{12}itshape}
usepackage{lipsum}

begin{document}
begin{abstract}
lipsum[1]
end{abstract}
end{document}

documentclass[a4paper]{article}
usepackage{geometry}
geometry{
    a4paper,
    total={210mm,297mm},
    left=30mm,
    top=30mm,
    right=30mm,
    bottom=30mm
}

usepackage[T1]{fontenc}
usepackage{lmodern}
usepackage{mathptmx}
usepackage[english]{babel}
usepackage{graphicx}
usepackage[colorinlistoftodos]{todonotes}
usepackage{kpfonts}
usepackage{amsmath,amsfonts,amssymb}
usepackage{tocloft}
usepackage{authblk}
usepackage{abstract}
usepackage{fontspec}
usepackage{titlesec}
usepackage{slantsc}
usepackage{bold-extra}

renewcommand{absnamepos}{flushleft}
setlength{absleftindent}{0pt}
setlength{absrightindent}{0pt}
renewcommand{abstractnamefont}{fontsize{13}{16}scshapeitshapebfseriesselectfontparskip6pt}
renewcommand{abstracttextfont}{fontsize{10}{12}itshape}
usepackage{lipsum}

begin{document}
begin{abstract}
vspace*{6pt}
noindent lipsum[1]
end{abstract}
end{document}