[Tex/LaTex] Change title fontsize and abstract fontsize

Question

I want to write an article with fontsize 11pt. I have problem to change fontsize of title is 14pt and abstract fontsize 9pt.

This is my code :

\documentclass[11pt,a4paper]{article}
\usepackage[left=3.00cm, right=2.00cm, bottom=2.00cm, top=2.00cm]{geometry}
\tolerance=1
\emergencystretch=\maxdimen
\hyphenpenalty=10000
\hbadness=10000
\RequirePackage[english,bahasa]{babel}
\RequirePackage{times}
\RequirePackage{setspace}
\RequirePackage{indentfirst}

\RequirePackage{graphicx,latexsym}
\RequirePackage{amssymb}
\RequirePackage{amsfonts}
\RequirePackage{amstext}
\RequirePackage{amsmath}
\RequirePackage{amsthm}
\RequirePackage{listings}
\RequirePackage{color}
\RequirePackage{float}
\RequirePackage{longtable}
\RequirePackage{enumerate}
\RequirePackage{multirow}
\RequirePackage[center,font=footnotesize,labelfont=bf,textfont=bf,labelsep=space,aboveskip=1.5ex,singlelinecheck=off]{caption}
\RequirePackage{pdfpages}
\RequirePackage{fancyhdr}
\RequirePackage{tikz}
\RequirePackage{cases}
\usepackage{ragged2e}
\usetikzlibrary{matrix,arrows,shapes.geometric}
\allowdisplaybreaks
\RequirePackage{natbib}
\bibliographystyle{plainnat}

\renewcommand{\baselinestretch}{1}
\parskip0.15cm

\renewcommand{\normalsize}{\fontsize{11bp}{12bp}\selectfont}
\frenchspacing

\usepackage{graphicx}
\usepackage{graphics}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{pgf,tikz}
%\usepackage[bahasa]{babel}
\usepackage{enumitem}
\tolerance=1
\emergencystretch=\maxdimen
\hyphenpenalty=10000
\hbadness=10000
\usepackage{graphicx}
\usepackage{graphics}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{pgf,tikz}
\usepackage[bahasa]{babel}
\usepackage{titlesec}
\titleformat{\section}
{\normalfont\fontsize{11}{15}\bfseries}{\thesection}{1em}{}
%\renewcommand{\thesection}{\thechapter\arabic{section}.}

\titleformat{\section}                                     
{\bfseries}
{\thesection.}{1em}{}
\titleformat{\subsection}                                   
{\slshape\bfseries}
{\thesubsection.}{1em}{}

\renewcommand{\thesubsection}{\thesection\arabic{subsection}}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{lemma}[theorem]{Lemma}%[section]
\newtheorem{definition}[theorem]{Definition}%[section]
\newtheorem{example}[theorem]{Example}
\begin{document}
\begin{center}
\textbf{TITLE, I WANT FONTSIZE 14pt}\\\vspace{0.3cm}
\textbf{Full name}\\\vspace{0.3cm}
\textit{Institution}\\\vspace{0.1cm}
\textit{e-mail: \textcolor{blue}{\underline{.....@yahoo.com}}}
\end{center}
\textbf{\textit{Abstract.}} I want abstract's fontsize 9pt\\ \\
\textit{\textbf{Keywords}: blabla1,blabla2.}
\vspace{-0.5cm}
\section{INTRODUCTION}\vspace{-0.45cm}
hello hello hello
\section{SECTION TWO}\vspace{-0.45cm}
\begin{theorem}
    theorem ...
\end{theorem}

\end{document}

and this is the result :

How to change fontsize of title and abstract?

Answer 1

The preamble is really a mess and also produces errors. Start with a minimal one and add only the packages you really need.

\documentclass[11pt,a4paper]{article}
\usepackage[left=3.00cm, right=2.00cm, bottom=2.00cm, top=2.00cm]{geometry}
\usepackage[english,bahasa]{babel}

\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{xcolor}
\usepackage{titlesec}

\usepackage{newtxtext,newtxmath} % not times

\titleformat{\section}                                     
  {\bfseries}
  {\thesection.}
  {1em}
  {}
\titleformat{\subsection}                                   
  {\slshape\bfseries}
  {\thesubsection.}
  {1em}
  {}

\newtheorem{theorem}{Theorem}

% change the abstract
\renewenvironment{abstract}{%
  \quotation
  \footnotesize
  \textbf{\textit{\abstractname.}} % with a normal space
}{\endquotation}


\begin{document}
\begin{center}
\fontsize{14}{17}\selectfont
\textbf{TITLE, I WANT FONTSIZE 14pt}

\vspace{0.3cm}

\normalsize

\textbf{Full name}

\vspace{0.3cm}

\textit{Institution}

\vspace{0.1cm}

\textit{e-mail: \textcolor{blue}{\underline{.....@yahoo.com}}}
\end{center}

\begin{abstract}\footnotesize
I want abstract's fontsize 9pt

\bigskip

\textit{\textbf{Keywords}: blabla1,blabla2.}
\end{abstract}

\section{INTRODUCTION}

hello hello hello

\section{SECTION TWO}

hello hello hello

\subsection{Subsection}

\begin{theorem}
    theorem ...
\end{theorem}

\end{document}

If you want less space after the section titles, act with \titlespacing, not with manual \vspace after them.

The settings \tolerance=1 and \hyphenpenalty=10000 just make for huge interword spaces and very low quality typesetting.