XeLaTeX giving me many gibberish errors when trying to compile beamer presentation

I am writing a beamer presentation and when I try to compile it with running xelatex chessboxing.tex chessboxing.pdf, everything goes fine until here:

! Missing $ inserted.
<inserted text>
                $
l.41 end{frame}

?

! LaTeX Error: Command $ invalid in math mode.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.41 end{frame}

?

! LaTeX Error: Command ttfamily invalid in math mode.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.41 end{frame}

?
! Missing } inserted.
<inserted text>
                }
l.41 end{frame}

?
! Missing endgroup inserted.
<inserted text>
                endgroup
l.41 end{frame}

?
! Missing endgroup inserted.
<inserted text>
                endgroup
l.41 end{frame}

?
! Undefined control sequence.
Url@FormatString ...ndafter UrlLeft Url@String
                                                  UrlRight m@th $
l.41 end{frame}

?
! Extra }, or forgotten $.
<recently read> }

l.41 end{frame}

?
! Missing $ inserted.
<inserted text>
                $
l.41 end{frame}

?
! Missing } inserted.
<inserted text>
                }
l.41 end{frame}

?
! Missing } inserted.
<inserted text>
                }
l.41 end{frame}

?
! Too many }'s.
beamer@doifinframe ...2.0}, от Wikimedia Commons}
                                                   end {beamer@frameslide}
l.41 end{frame}

?

! LaTeX Error: begin{document} ended by end{beamer@framepauses}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.41 end{frame}

?
! Extra endgroup.
<recently read> endgroup

l.41 end{frame}

?
! Too many }'s.
endbeamer@frameslide ...amer@framepauses}egroup
                                                  ifx beamer@frametitle @...
l.41 end{frame}

?
! Undefined control sequence.
endbeamer@frameslide ...box else beamer@zoomer
                                                  fi beamer@undolabels be...
l.41 end{frame}

?

! LaTeX Error: begin{document} ended by end{beamer@frameslide}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.41 end{frame}

?
! Extra endgroup.
<recently read> endgroup

l.41 end{frame}

?

I just press enter and it compiles, but then my presentation hase some issues. Also, I checked some of the errors and they all seem like gibberish. Here is my LaTeX file:

documentclass[bulgarian]{beamer}
usepackage{hyperref}
usepackage{enumitem}
usepackage{blindtext}
usepackage{babel}
babelfont{rm}{FreeSans}
setmainfont{FreeSans}
setsansfont{FreeSans}
setmonofont{FreeMono}
usetheme{Bergen}
usecolortheme{seagull}
title{Шахбокс}
author{Явор Узунов 5А клас}
begin{document}
begin{frame}
frametitle{Шахбокс}
Шахбоксът е хибриден спорт. В него се играе бокс и шах. Хубав е, защото развива и мозъка, и здравословното тяло.
includegraphics{/home/yav/Schachboxen1.jpg}

{tiny"Schachboxen1.jpg" от WCBO, CC BY 3.0 DE url{https://creativecommons.org/licenses/by/3.0/de/deed.en}, от Wikimedia Commons}
end{frame}



begin{frame}
frametitle{Правила}
% section[Section]{Рундове и печелене}
Има 6 рунда бърз шах и 5 рунда бокс. Започва се с шаха. Обявява се победа при:
begin{itemize}[noitemsep]
item нокаут
item мат
item свършване на времето на играч в бърз шах (9 минути)
item по преценка на съдията
item отказ от участие
end{itemize}
Ако шахматните игри завършат с равен резултат, побеждава този, който има повече точки в бокса, а ако и там е равно, печели този, който е играл с черните фигур>
% section[Section]{Класове по тежест}
includegraphics[height=2cm]{/home/yav/Chess_Boxing_2007_(3).jpg}includegraphics[height=2cm]{/home/yav/Chess_Boxing_2007_(4).jpg}

{tiny Chess_Boxing_2007_(3).jpg и Chess_Boxing_2007_(4).jpg от Sascha Pohflepp, CC BY 2.0 url{https://creativecommons.org/licenses/by/2.0}, от Wikimedia Com>
end{frame}
end{document}