Changing citation language in latex - latex

Question

I am trying to include citations APA style in my latex document which is written in dutch. However, the citations appear as
author e.a. (year)
instead of
author et al. (year)
The first is probably some translation, but in dutch is is very common to still use et al. How do I change the citations in text to et al.?
\documentclass[dutch]{article}
\usepackage[utf8]{inputenc}
\usepackage[dutch]{babel}
\usepackage{csquotes}
\usepackage[style=apa, backend=bibtex]{biblatex}
\addbibresource{Refrences.bib}
\begin{document}
\begin{otherlanguage}{dutch}
Dit is een test. \cite{Schleigh2015}. \cite{Slater2015}
\bibliography{bibliography}
\printbibliography
\end{otherlanguage}
\end{document}
output:
Dit is een test. Schleigh e.a., 2015. Slater e.a., 2015
Also, i just discoverd that apperently this apa style does not print an "&" when more than three authors are present. Instead in prints the word "and", which is not apa.
Author1, Author2 AND Author3
which should be:
Author1, Author2 & Author3

Answer 1

Luckily you use the biblatex package, this makes it easy to adjust the string:
\documentclass[dutch]{article}
\usepackage[utf8]{inputenc}
\usepackage[dutch]{babel}
\usepackage{csquotes}
\usepackage[style=apa, backend=biber]{biblatex}
\addbibresource{biblatex-examples.bib}
\DefineBibliographyStrings{dutch}{
andothers = {et\addabbrvspace al\adddot},
andmore = {et\addabbrvspace al\adddot},
}
\begin{document}
Dit is een test. \cite{aksin}.
\printbibliography
\end{document}
Some other comments about your code:
apa styles requires the biber backend. With your attempt to use it with biblatex, you should have gotten an error messages telling you that. Please do not ignore error messages
your are mixing syntaxes from two different bibliography tools. \addbibresource{...} and \printbibliography are correct syntax for biblatex. \bibliography{bibliography} is not.
with \usepackage[dutch]{babel} you already changed the main language of your document to dutch, \begin{otherlanguage}{dutch}...\end{otherlanguage} is not necessary