Bib Formatting Question

Question

so I've been trying to build a framework for my bibliography, for later use. However I fail at formatting internet sources.

Here is what they should look like:

This is what it does look like:

So basically the following elements are wrong: - title must not be italic (probably because titles in the source "book" are supposed to be italic and online and article titles shouldn't (it does work for articles, meaning article titles are already shown as plain and not italic, but it does not work for online sources.)

• institution/organisation must be in small caps
• website title must be italic (is not shown at all in my case)
• the URL should not precede with "URL:"
• instead of saying "besucht am" it should state "letzter Abruf:"

Furthermore I figured, that in one case the online source entry is not formatted correctly at all and crossing the page borders.

Retry:

    \documentclass[12pt,a4paper,headings=standardclasses,numbers=noenddot]{scrreprt}
\usepackage{showframe}
\usepackage{graphicx}
\graphicspath{ {./images/} }
\usepackage[left=2.50cm, right=2.50cm, top=2.50cm, bottom=2.00cm]{geometry}
\usepackage[onehalfspacing]{setspace}
\usepackage[main=ngerman, english]{babel}
\usepackage[babel, german=quotes]{csquotes}
\usepackage[ngerman]{isodate}
\usepackage[ngerman]{datetime}

 \usepackage[
    backend=biber,
    style=authoryear,
    sorting=nyvt
  ]{biblatex}
  \addbibresource{backmatter/sample.bib}
\renewcommand{\mkbibnamefamily}[1]{\textsc{#1}}
\renewcommand{\labelnamepunct}{\addcolon\space}
\DeclareFieldFormat{postnote}{#1}
\DeclareFieldFormat{multipostnote}{#1}
\renewcommand\postnotedelim{\addcolon\addspace}
\usepackage{url}
\urlstyle{same}

\begin{document}
\printbibliography[heading=bibintoc,title={Literaturverzeichnis}]
\end{document}

Answer 1

As discussed in Omit Vol and Issue/No? we are following the guidelines of the IOA Bonn https://www.ioa.uni-bonn.de/de/studium/materialien/formalregeln_ioa.pdf.

The guidelines for @online sources can be found in §10.2.12 Artikel aus dem Internet. There is an inconsistency between the explanatory text and the example: The page numbers (which I would say are not needed anyway: the exact location will be pinpointed in the citation) are shown before editor and page title in the example, but the explanatory text places them after that...

By default biblatex does not support a overall website/webpage title for @online, but we can use maintitle for that. If we then tweak the output of the "editor" a bit, we can get

\documentclass[ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

 \usepackage[
    backend=biber,
    style=authoryear,
    sorting=nyvt
  ]{biblatex}

\renewcommand{\mkbibnamefamily}[1]{\textsc{#1}}

\DeclareDelimFormat{nametitledelim}{\addcolon\space}

\DeclareFieldFormat[online]{title}{#1}

\urlstyle{same}
\DeclareFieldFormat{url}{\url{#1}}
\DefineBibliographyStrings{german}{
  urlseen = {letzter Abruf},
}
\DeclareFieldFormat{urldate}{\mkbibparens{\bibstring{urlseen}\addcolon\space#1}}


\newbibmacro{online:editor+maintitle}{%
  \printnames{editor}%
  \setunit*{\addcolon\space}%
  \usebibmacro{maintitle}%
}

\usepackage{xpatch}

\xpatchbibdriver{online}
  {\usebibmacro{byeditor+others}}
  {\usebibmacro{online:editor+maintitle}}
  {}{}

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@online{fluechter,
  author    = {Flüchter, Winfried},
  date      = {1997},
  title     = {Tokyo  quo  vadis?  Chancen  und  Grenzen  (?)  metropolitanen Wachstums},
  pages     = {1-39},
  editor    = {{Universität Duisburg-Essen}},
  maintitle = {DuEPublico},
  url       = {https://duepublico.uni-duisburg-essen.de/servlets/DerivateServlet/Derivate-5290/dao1598.pdf},
  urldate   = {2018-10-23}, 
}
\end{filecontents}

\addbibresource{\jobname.bib}


\begin{document}
\cite{fluechter}
\printbibliography
\end{document}

In the question you also complained about the URLs running into the margin. URLs are a huge challenge for LaTeX because they don't behave like normal words (which the hyphenation algorithm can deal with), so line breaks in URLs are complicated beasts. By default only breaks after certain "punctuation" characters like ., /, : are allowed. There are approaches to solve these issues, but since line breaking is such a delicate task it could well be that answers that worked great for other people don't seem to work for you.

As already explained, LaTeX allows breaks in URLs only after a small set of characters. You can tell it to allow breaks after other characters (like letters or numbers) as well. See Line breaks of long URLs in biblatex bibliography? for example. Keep in mind, however, that LaTeX does not break the URLs at morpheme boundaries or hyphenation points of the words a human can make out in the URL, it will just blindly break the URL where it makes sense for the line length. So you may well end up with

https://www.eas-
tasiaonline.com

or other unfortunate break points if you allow line breaks after all letters.

Similar approaches are explained in Forcing linebreaks in \url, but Line breaks of long URLs in biblatex bibliography? offers a finer control over things and was written specifically for biblatex.

It may turn out that it is just too hard to properly break the URL in a reference and in that case you can look at How to adjust the breaking in the bibliography? for different approaches to improve line breaks in the bibliography. Since the bibliography does not contain running prose, finding good hyphenation and break points is a challenge and you may bail out of that by telling LaTeX to set the bibliography left aligned (ragged right) instead of fully justified (aligned on both margins).

As mentioned in the comments, we can only offer concrete help for a URL breaking problem if we get to see code that reproduces the exact issue. Otherwise we have to point to the generic solutions I outlined here.