textbf and textit does not work

So I have a main.tex that looks like this:

documentclass[a4paper,11pt]{book}
usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}
usepackage{lmodern}
usepackage{hyperref}
usepackage{graphicx}
usepackage[danish, english]{babel}
usepackage{xspace}

newenvironment{dedication}
{
   %cleardoublepage
   thispagestyle{empty}
   vspace*{stretch{1}}
   hfillbegin{minipage}[t]{0.66textwidth}
   raggedright
}
{
   end{minipage}
   vspace*{stretch{3}}
   clearpage
}

makeatletter
renewcommand{@chapapp}{}% Not necessary...
newenvironment{chapquote}[2][2em]
  {setlength{@tempdima}{#1}%
   defchapquote@author{#2}%
   parshape 1 @tempdima dimexprtextwidth-2@tempdimarelax%
   itshape}
  {parnormalfonthfill-- chapquote@authorhspace*{@tempdima}parbigskip}
makeatother

title{Huge textbf{De Maskerede}}
author{textsc{Niklas}}

begin{document}

frontmatter
maketitle
tableofcontents
mainmatter

{fontfamily{times}selectfont
chapter{textit{Prolog}}
input{Prolog/Post.tex}

end{document}

And my post.tex file looks like this:

hi this is textbf{bold}

When I do a textbf inside the main.tex it works (like the title), but when I do a textbf in one of the input files (like input{Prolog/Post.tex}), it does not work. I can’t figure out the reason why.

Best regards
Niklas