How can I make longtable behave like table?

Like this?

Document class svjour3 default settings define small font size (only) for table floats contents and has not define boldface font for caption labels, so if you like (anyway) to has it, you need to add caption package and with it overwrite its default settings. To have longtable caption left align, you need to add singlelinecheck=false to caption package options. For smaller fonts in longtable, you need to enclose it in group which has small font size.

Beside aforementioned changes in MWE below are used horizontal lines define in the booktabs package:

RequirePackage{fix-cm}
documentclass[smallextended]{svjour3}       % onecolumn (second format)
usepackage{booktabs, longtable, multirow}
usepackage[singlelinecheck=false,labelfont=bf]{caption}
usepackage{lipsum}

begin{document}
lipsum[1]
begin{table}[ht]
    caption{With table}
    label{tab:1}
    begin{tabular}{llllllll}
    toprule
C1 & C2 & C3 & C4 & C5 & C6 & C7 & C8 
    midrule
multirow{5}{*}{First}
    & multirow{5}{*}{1}
        & A & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        &   & B & 0.00 & 0.00 & 0.00 & 0.0 & 0.00 
        &   & C & 0.0 & 0.00 & 0.00 & 0.00 & 0.00 
        &   & D & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        &   & E & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
    %...
    bottomrule
    end{tabular}
end{table}

begingroup
small
begin{longtable}[l]{llllllll}
    caption{With longtable}
    label{tab:1}
    toprule
C1 & C2 & C3 & C4 & C5 & C6 & C7 & C8 
    midrule
multirow{5}{*}{First} 
    & multirow{5}{*}{1} 
        & A & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        &   & B & 0.00 & 0.00 & 0.00 & 0.0 & 0.00 
        &   & C & 0.0 & 0.00 & 0.00 & 0.00 & 0.00 
        &   & D & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        &   & E & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
    %...
    bottomrule
end{longtable}
endgroup
end{document}

You can redefine the internal command that longtable uses for the caption, according to what svjour3 does.

I also define a new environment for the adaptation of longtable to Springer's style.

%%%%%%%%%%%%%%%%%%%%%%% file template.tex %%%%%%%%%%%%%%%%%%%%%%%%%
%
% This is a general template file for the LaTeX package SVJour3
% for Springer journals.          Springer Heidelberg 2010/09/16
%
% Copy it to a new file with a new name and use it as the basis
% for your article. Delete % signs as needed.
%
% This template includes a few options for different layouts and
% content for various journals. Please consult a previous issue of
% your journal as needed.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
RequirePackage{fix-cm}
%
%documentclass{svjour3}                     % onecolumn (standard format)
%documentclass[smallcondensed]{svjour3}     % onecolumn (ditto)
documentclass[smallextended]{svjour3}       % onecolumn (second format)
%documentclass[twocolumn]{svjour3}          % twocolumn
%
smartqed  % flush right qed marks, e.g. at end of proof
%
usepackage{graphicx}
%
% usepackage{mathptmx}      % use Times fonts if available on your TeX system
%
% insert here the call for the packages your document requires
%usepackage{latexsym}
usepackage{amsmath}
usepackage{algpseudocode}
usepackage{algorithm}
usepackage{multirow}
usepackage{longtable}
usepackage{booktabs}
% etc.
%
% please place your own definitions here and don't use def but
% newcommand{}{}
%
% Insert the name of "your journal" with
% journalname{myjournal}
%

newenvironment{svlongtable}[1]
 {smallbegin{longtable}[l]{#1}}
 {end{longtable}}
makeatletter
renewcommand{LT@makecaption}[3]{%
  LT@mcol LT@cols {@{}l@{}}{%
    hbox toz@ {%
      parbox [t]LTcapwidth {%
        sbox @tempboxa {#1{textbf{#2}}quad#3}%
        ifdim wd @tempboxa >hsize
          #1{textbf{#2}}quad#3
        else
          hbox tohsize {%
            box @tempboxa hfil
          }%
        fi
        endgraf
        vskiptabcapgap
      }%
      hss
    }%
  }%
}
makeatother

begin{document}

title{Insert your title here%thanks{Grants or other notes
%about the article that should go on the front page should be
%placed here. General acknowledgments should be placed at the end of the article.}
}
subtitle{Do you have a subtitle? If so, write it here}

%titlerunning{Short form of title}        % if too long for running head

author{First Author         and
        Second Author %etc.
}

%authorrunning{Short form of author list} % if too long for running head

institute{F. Author at
              first address 
              Tel.: +123-45-678910
              Fax: +123-45-678910
              email{[email protected]}           %  
%             emph{Present address:} of F. Author  %  if needed
           and
           S. Author at
              second address
}

date{Received: date / Accepted: date}
% The correct dates will be entered by the editor


maketitle

begin{abstract}
Insert your abstract here. Include keywords, PACS and mathematical
subject classification numbers as needed.
keywords{First keyword and Second keyword and More}
% PACS{PACS code1 and PACS code2 and more}
% subclass{MSC code1 and MSC code2 and more}
end{abstract}

section{Introduction}
label{intro}
Your text comes here. Separate text sections with
section{Section title}
label{sec:1}
Text with citations cite{RefB} and cite{RefJ}.
subsection{Subsection title}
label{sec:2}
as required. Don't forget to give each section
and subsection a unique label (see Sect.~ref{sec:1}).
paragraph{Paragraph headings} Use paragraph headings as needed.
begin{equation}
a^2+b^2=c^2
end{equation}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Here

begin{table}[htp]
    caption{With table}
    label{tab:1}
    begin{tabular}{llllllll}
        toprule
        C1 & C2 & C3 & C4 & C5 & C6 & C7 & C8 
        midrule
        multirow{5}{*}{First} & multirow{5}{*}{1} & A & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        & & B & 0.00 & 0.00 & 0.00 & 0.0 & 0.00 
        & & C & 0.0 & 0.00 & 0.00 & 0.00 & 0.00 
        & & D & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        & & E & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
        %...
        bottomrule
    end{tabular}
end{table}

begin{svlongtable}{llllllll}
    caption{With longtable}
    label{tab:2}
    toprule
    C1 & C2 & C3 & C4 & C5 & C6 & C7 & C8 
    midrule
    endfirsthead
    multirow{5}{*}{First} & multirow{5}{*}{1} & A & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 *
    & & B & 0.00 & 0.00 & 0.00 & 0.0 & 0.00 *
    & & C & 0.0 & 0.00 & 0.00 & 0.00 & 0.00 *
    & & D & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 *
    & & E & 0.00 & 0.00 & 0.00 & 0.00 & 0.00 
    %...
    bottomrule
end{svlongtable}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%begin{acknowledgements}
%If you'd like to thank anyone, place your comments here
%and remove the percent signs.
%end{acknowledgements}


% Authors must disclose all relationships or interests that 
% could have direct or potential influence or impart bias on 
% the work: 
%
% section*{Conflict of interest}
%
% The authors declare that they have no conflict of interest.


% BibTeX users please use one of
%bibliographystyle{spbasic}      % basic style, author-year citations
%bibliographystyle{spmpsci}      % mathematics and physical sciences
%bibliographystyle{spphys}       % APS-like style for physics
%bibliography{}   % name your BibTeX data base

% Non-BibTeX users please use
begin{thebibliography}{}
%
% and use bibitem to create references. Consult the Instructions
% for authors for reference list style.
%
bibitem{RefJ}
% Format for Journal Reference
Author, Article title, Journal, Volume, page numbers (year)
% Format for books
bibitem{RefB}
Author, Book title, page numbers. Publisher, place (year)
% etc
end{thebibliography}

end{document}
% end of file template.tex

Note how I disabled the possibility to have unwanted page breaks.