! Package pgfkeys Error: I do not know the key '/tikz/"f"' and I am going to ignore it. Perhaps you misspelled it.

documentclass[
    oneside,openright,titlepage,numbers=noenddot,headinclude,%1headlines,
    %footinclude=true,
    cleardoublepage=empty,
    dottedtoc, % Make page numbers in the table of contents flushed right with dots leading to them
    BCOR=5mm,paper=a4,fontsize=11pt, % Binding correction, paper type and font size
    ngerman,american, % Languages, change this to your language(s)
    ]{scrreprt}

% Includes the file which contains all the document configurations and packages - make sure to edit this file
input{classicthesis-config}

 begin{document}
 begin{center}
    begin{tikzcd}
                U
                arrow[r,hook, "f"]
              & V
end{tikzcd}
end{center}
end{document}

documentclass[
    oneside,openright,titlepage,numbers=noenddot,headinclude,%1headlines,
    %footinclude=true,
    cleardoublepage=empty,
    dottedtoc, % Make page numbers in the table of contents flushed right with dots leading to them
    BCOR=5mm,paper=a4,fontsize=11pt, % Binding correction, paper type and font size
    ngerman,american, % Languages, change this to your language(s)
    ]{scrreprt}

% Includes the file which contains all the document configurations and packages - make sure to edit this file
input{classicthesis-config}

 begin{document}
 begin{center}
    begin{tikzcd}
                U
                arrow{r}{f}
              & V
end{tikzcd}
end{center}
end{document}