Journal biblatex citation problem

Question

I want to make citations and references exactly like what is requested in the picture:

.

I used the template from the journal:

\documentclass[USenglish]{article}

\usepackage[T1]{fontenc}
\usepackage{lmodern}

\usepackage[utf8]{inputenc}%(only for the pdftex engine)
%\RequirePackage[no-math]{fontspec}[2017/03/31]%(only for the luatex or the xetex engine)
\usepackage[small]{dgruyter}
\usepackage{microtype}


%\usepackage{natbib}
%\setcitestyle{numbers}
\usepackage[backend=bibtex,citestyle=authoryear-comp,bibstyle=authoryear]{biblatex}
\addbibresource{SAGMB_submit_Fan}

\begin{document}

%  \articletype{}

  \author*[1]{a1}
  \author[2]{a2}
  \author[1]{a3} 
  \runningauthor{runningauthor}
  \affil[1]{affil1}
  \affil[2]{affil2}
  \title{Title}
  \runningtitle{runningtitle}
  %\subtitle{}
  \abstract{Abstract}
  \keywords{}
  %\classification[PACS]{}
  %\communicated{}
  %\dedication{}
  %\received{}
  %\accepted{}
  \journalname{}
  \journalyear{}
  \journalvolume{}
  \journalissue{}
  \startpage{1}
  %\aop
  \DOI{}

\maketitle

\section{Introduction} 

Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean  massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec


Citation 1: \textcite{witten2009penalized} and citation 2: \textcite{eckart1936approximation}.


\begin{acknowledgement}
  ...
\end{acknowledgement}

%\bibliographystyle{authoryear}
%\bibliography{SAGMBsubmit22.bib}
\printbibliography
\end{document}

To use this template, you have to install a package called dgruyter and it's installed as according to their description:

To get the package style file 'dgruyter.sty' and the index style files 'dgruyter.ist' and 'dgruyter.xdy' execute: latex dgruyter.ins

The minimum requirement to use the package is to have dgruyter.sty and dgruyter.ist/dgruyter.xdy (as well as the logo and vignette files) in a directory where TeX can find it.

The dgruyter.ins file is:

% -----------------------------------------------------------------
% File:       dgruyter.ins
% Author:     le-tex publishing services
% Maintainer: le-tex publishing services
%
% This file is part of the dgruyter package for preparing
% books for Walter de Gruyter GmbH.
%
%       Copyright (C) 2015, 2016, 2017 Walter de Gruyter GmbH
%
% -----------------------------------------------------------------
% This file will generate fast loadable files and documentation
% driver files from the doc files in this package when run through
% LaTeX or TeX.
%
% The file 'README' contains a list of all the files as well
% directions for installation of this package.
% -----------------------------------------------------------------

\def\filedate{2017/09/19}

\input docstrip.tex
\keepsilent

\askforoverwritefalse

\preamble
-----------------------------------------------------------------
Author:     le-tex publishing services
Maintainer: le-tex publishing services

This file is part of the dgruyter package for preparing
books for Walter de Gruyter GmbH.

      Copyright (C) 2015, 2016, 2017 Walter de Gruyter GmbH
-----------------------------------------------------------------
\endpreamble

\declarepostamble\istpost
\endpostamble

\generate{\file{dgruyter.sty}{\from{dgruyter.dtx}{package}}
          \usepostamble\istpost
          \file{dgruyter.ist}{\from{dgruyter.dtx}{ist}}
          \protect\def\MetaPrefix{}%
          \nopreamble\nopostamble
          \file{dgruyter.xdy}{\from{dgruyter.dtx}{xdy}}}

{\obeyspaces
\Msg{***********************************************************}%
\Msg{*                                                         *}%
\Msg{* To finish the installation you have to move the         *}%
\Msg{* following files into a directory searched by TeX:       *}%
\Msg{*                                                         *}%
\Msg{*    dgruyter.sty                                         *}%
\Msg{*    dgruyter.ist                                         *}%
\Msg{*    dgruyter.xdy                                         *}%
\Msg{*    (as well as the logo and vignette files)             *}%
\Msg{*                                                         *}%
\Msg{* To produce the documentation run the file dgruyter.dtx  *}%
\Msg{* through LaTeX.                                          *}%
\Msg{*                                                         *}%
\Msg{* Happy TeXing!                                           *}%
\Msg{*                                                         *}%
\Msg{***********************************************************}}
\endbatchfile

And my bib file looks like:

@article{witten2009penalized,
  title={A penalized matrix decomposition, with applications to sparse principal components and canonical correlation analysis},
  author={Witten, Daniela M and Tibshirani, Robert and Hastie, Trevor},
  journal={Biostatistics},
  volume={10},
  number={3},
  pages={515--534},
  year={2009},
  publisher={Oxford University Press}
}


@article{eckart1936approximation,
  title={The approximation of one matrix by another of lower rank},
  author={Eckart, Carl and Young, Gale},
  journal={Psychometrika},
  volume={1},
  number={3},
  pages={211--218},
  year={1936},
  publisher={Springer}
}

Those logos are too many, so I think I can skip them here anyway.

The output I get is:

After all these, I found the citation part does not work, as the citation 1 has three names whereas it should be like "onename, et al.(year)" according to the journal request #3 point. While the reference part worked. How to solve this issue?