Where can I find a usermanual and quickguide for dynamics nav 2013 R2
Welcome to forum!
Manuals for NAV do not exist as such - have never existed regardless of version, even for the very first ones ~20 years ago.
If you (your company) are a NAV enduser with active Service plan, you are eligible to get access to CustomerSource. This is a special MS extranet for Dynamics customers, containing tons of different materials - among them courseware, whitepapers, guides etc etc.
If you work for MS Partner company, then you can access PartnerSource, but in this case training materials must be paid for additionaly (MS Training Partners only get them for free).
Unfortunately, if you are none of the above, you will not be able to access these sites and your only source will be only Help system - or you can buy some books, links of most worthy of them are collected in this DUG page.
Please log in to partner source and go to download page.