Hyperref package causing error: You can't use a prefix with \begingroup

I am getting the error

You can't use a prefix with `\begingroup'. \begin{document}

when I include hyperref package.

Below are the package I am using:

\RequirePackage[l2tabu, orthodox]{nag}
\documentclass

\DeclareRobustCommand\mbseries{\fontseries{mb}\selectfont}
\DeclareTextFontCommand{\textmb}{\mbseries}


% chosse the German or English package
\usepackage{graphicx,pdflscape}
\usepackage{hyperref}
\usepackage{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[ngerman, english]{babel}
\usepackage{lmodern}
\usepackage{microtype}
\usepackage{amsfonts}
\usepackage{tikz-qtree}
\usepackage[backend=bibtex,style=numeric]{biblatex}
\usepackage{adjustbox}
\usepackage{makecell}
\renewcommand\theadfont{\bfseries}
\usepackage{bera}% optional: just to have a nice mono-spaced font
\usepackage{floatflt}
\usepackage{float}
\usepackage{listings}
\usepackage{xcolor}

\colorlet{punct}{red!60!black}
\definecolor{delim}{RGB}{20,105,176}
\colorlet{numb}{magenta!60!black}
\lstdefinelanguage{json}{
    basicstyle=\tiny\ttfamily,
    %numbers=left,
    %numberstyle=\scriptsize,
    keywordstyle=\bfseries,
    morekeywords={begin, end, if, else, while, for, then, do},
    stepnumber=1,
    numbersep=8pt,
    showstringspaces=false,
    breaklines=true,
    frame=trbl, % draw a frame at the top, right, left and bottom of the listing
    frameround=tttt, % make the frame round at all four corners
    %backgroundcolor=\color{background},
    literate=
    *{0}{{{\color{numb}0}}}{1}
    {1}{{{\color{numb}1}}}{1}
    {2}{{{\color{numb}2}}}{1}
    {3}{{{\color{numb}3}}}{1}
    {4}{{{\color{numb}4}}}{1}
    {5}{{{\color{numb}5}}}{1}
    {6}{{{\color{numb}6}}}{1}
    {7}{{{\color{numb}7}}}{1}
    {8}{{{\color{numb}8}}}{1}
    {9}{{{\color{numb}9}}}{1}
    {:}{{{\color{punct}{:}}}}{1}
    {,}{{{\color{punct}{,}}}}{1}
    {\{}{{{\color{delim}{\{}}}}{1}
    {\}}{{{\color{delim}{\}}}}}{1}
    {[}{{{\color{delim}{[}}}}{1}
    {]}{{{\color{delim}{]}}}}{1}
}

\newcommand{\getmydate}{
  \ifcase\month%
    \or Januar\or Februar\or M\"arz%
    \or April\or Mai\or Juni\or Juli%
    \or August\or September\or Oktober%
    \or November\or Dezember%
  \fi\ \number\year%
}


\usepackage{todonotes}

\addbibresource{Template.bib}
\begin{document} % I get error in this line

It would be great help if anyone could suggest me why I have this error? I have searched in many forums but could not understand the problem.

while this is true it is unlikely to be related to the error message in the question.

@DavidCarlisle -- the error message in the question doesn't seem to be generated when the example is run unchanged; a different, but equally unhelpful message is what happened when i tried. but the purported removal of amsfonts solving the problem is equally ridiculous. simply adding a real document class got rid of the errors, although i can't say for sure that the result is what was wanted.

no, that did not solve any problem in the posted document.