[Tex/LaTex] hyperref vs includepdf

Question

\documentclass[12pt,a4paper]{mwrep}
\usepackage{polski}
\usepackage[cp1250]{inputenc}
\usepackage{pdfpages}
\usepackage[hidelinks]{hyperref}
\renewcommand\baselinestretch{1.5}

\usepackage{etoolbox}
\patchcmd{\thebibliography}{*}{}{}{}

\makeatletter
\pretocmd{\tableofcontents}{%
  \if@openright\cleardoublepage\else\clearpage\fi
  \pdfbookmark[0]{\contentsname}{toc}%
}{}{}%
\makeatother

\begin{document}
%\begin{titlepage}
%\includepdf[pages=1-]{titlepage.pdf}
%\end{titlepage}
\tableofcontents
\chapter{A}
a\dots
\chapter{B}c\dots
\chapter{D}
d\dots
\chapter{E}
e\dots

\begin{thebibliography}{999}
\bibitem{bib1}Author:
\emph{Title},
Publisher, Year
\end{thebibliography}
\end{document}

Everything works good, I have nice links in pdf viewer. But when I uncomment three lines with includepdf I got errors when trying to compile. titlepage.pdf contains two pages but I don't think this is relevant.

Second question, how can I add something to bookmars (generated by hyperref)? I want to add ToC as well as first page of titlepage.pdf.

Also, adding titlepage.pdf brokes page numeration in pdf viewer (bookmarks). When I try to go to page 7, I to to page 5 instead. Can it be fixed? (I know it is the result of adding two extra pages at the beginning).

Also, hyperref changes Polish letters.
I have chapter Wstęp but in bookmarks there is Wstep.
Can it be fixed?

EDIT:
Bookmark to ToC solved.

EDIT 2:
One more thing that I need is adding included pdf's first page to bookmarks.

Answer 1

If the "errors" are like

pdfTeX warning
 (ext4): destination with the same identifier (name{page.1}) has been already used, duplicate ignored

then they are solved by saying

\begin{document}
\pagenumbering{Alph}
\begin{titlepage}
\includepdf[pages=1-]{titlepage.pdf}
\end{titlepage}
\pagenumbering{arabic}
\tableofcontents

The reason is that hyperref finds two "page 1", which is not the case if we order LaTeX to number with letters the first two pages.