Tukukkk

I facing problem with the following codes

documentclass[a4paper,10pt]{article}

usepackage[T1]{fontenc}



usepackage{geometry}

geometry{left=2cm,right=2cm,top=1.5cm,bottom=1.5cm}



usepackage{pifont}

usepackage{sectsty}



usepackage{graphicx}

usepackage{amsmath,amsfonts,amsthm}



usepackage[colorlinks=true,linkcolor=blue,urlcolor=blue]{hyperref}



frenchspacing

sectionfont{%

  fontfamily{phv}bfseries

  sectionrule{0pt}{0pt}{-5pt}{1pt}%

}

pagestyle{empty}



    begin{document}



   section*{Academic Qualifications}

   begin{tabular}{rl}

   textsc{Dec.2016-Now :}

    &PhD Student in ........., textbf{Faculty of Sciences of ......}, 

     ......... spaces.\

  & Ongoing thesis title: On extreme points of the joint numerical range of 

     commuting normal operators,.\

  multicolumn{2}{c}{} \   

   textsc{October 2016 :}

  & Master Thesis in ........ at the textbf{Faculty of Sciences of 

    ........}, ...........

   end{tabular}

    end{document}

After compilation I get

Just use tabularx with an X column.

I suggest to you also to get rid of the :s. At least don't leave a blank between the word and the :, in my opinion, it is ugly and, as far as I know, it is not used in English.

documentclass[a4paper,10pt]{article}

usepackage[T1]{fontenc}



usepackage{geometry}

geometry{left=2cm,right=2cm,top=1.5cm,bottom=1.5cm}



usepackage{pifont}

usepackage{sectsty}

usepackage{tabularx}

usepackage{graphicx}

usepackage{amsmath,amsfonts,amsthm}



usepackage[colorlinks=true,linkcolor=blue,urlcolor=blue]{hyperref}



frenchspacing

sectionfont{%

  fontfamily{phv}bfseries

  sectionrule{0pt}{0pt}{-5pt}{1pt}%

}

pagestyle{empty}



    begin{document}



   section*{Academic Qualifications}

   begin{tabularx}{linewidth}{rX}

   textsc{Dec.2016-Now}

    &PhD Student in ........., textbf{Faculty of Sciences of ......}, 

     ......... spaces.\

  & Ongoing thesis title: On extreme points of the joint numerical range of 

     commuting normal operators,.\

  multicolumn{2}{c}{} \   

   textsc{October 2016}

  & Master Thesis in ........ at the textbf{Faculty of Sciences of 

    ........}, ...........

   end{tabularx}

    end{document}