How to cite with only year inside brackets, and not the name? [duplicate]

Question

I would like to cite with only the year within parentheses, however, the result is that both name and year come within parentheses.

E.g. (Breusch, 1978), but I'd like this to be Breusch (1978).

I have used the following code:

\usepackage[round]{natbib}
\usepackage{csquotes}
\usepackage[
  backend=biber,
  style=ext-authoryear,
  backref=true,
  doi=false,
  isbn=false,
  url=false,
  articlein=false,
  dashed=false,
  introcite=plain,
]{biblatex}
\usepackage{hyperref}
\hypersetup{colorlinks,linkcolor={black},citecolor={black},urlcolor={red}}  

\DeclareFieldFormat{bbx@introcite}{\mkbibbrackets{#1}}
\DeclareDelimFormat[bbx@introcite]{nameyeardelim}{\addcomma\space}
\UndeclareInnerCiteDelims{bbx@introcite}
\renewcommand{\bibopenbracket}{(}
\renewcommand{\bibclosebracket}{)} % felicitaaaaaaaaaaaaaaaaaaaa
%\renewcommand*{\introcitepunct}{\quad} omg finally, questa fa le parentisi è butto da vedere anche [] adiossssss

\setlength\bibitemsep{1.5\itemsep}

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

\DeclareOuterCiteDelims{cite}{\bibopenbracket}{\bibclosebracket}

\DeclareFieldFormat{linkallcite}{%
  \DeclareFieldFormat{bibhyperref}{##1}%
  \bibhyperref{#1}%
}
\AtIntrocite{\DeclareFieldFormat{linkallcite}{#1}}

\letbibmacro{cite:orig}{cite}
\renewbibmacro{cite}{%
  \printtext[linkallcite]{%
    \usebibmacro{cite:orig}}}

\DeclareDelimFormat{nameyeardelim}{\addcomma\space}

\DefineBibliographyStrings{german}{
  andothers    = {{et\,al\adddot}},
  backrefpage  = {zitiert auf Seite:},
  backrefpages = {zitiert auf Seiten:},
}



\addbibresource{biblio.bib}