It seems you are using the template here on overleaf. There we can find the definitions of the commands you used but did not show us :-((
The resulting pdf you see is the following, where I marked the issue with the red arrow: the black is overlapping the margin and that results in the overful message.

The used command \EducationEntry takes four parameter, so you can (better have to) shorten the title text and move in persian into the third parameter like:
\EducationEntry{"Maria Mitchel" (Women in Science) by "Dale Anderson"}{Aug 2015} % in Persian
{in Persian3}{in Persian4}
I suggest you use only the title of the translated books as first parameter and move the other parts to parameter 3 or 4.
With the following complete code
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% LaTeX Template: Curriculum Vitae
%
% Source: http://www.howtotex.com/
% Feel free to distribute this template, but please keep the
% referal to HowToTeX.com.
% Date: July 2011
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% How to use writeLaTeX:
%
% You edit the source code here on the left, and the preview on the
% right shows you the result within a few seconds.
%
% Bookmark this page and share the URL with your co-authors. They can
% edit at the same time!
%
% You can upload figures, bibliographies, custom classes and
% styles using the files menu.
%
% If you're new to LaTeX, the wikibook is a great place to start:
% http://en.wikibooks.org/wiki/LaTeX
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[paper=a4,fontsize=11pt]{scrartcl} % KOMA-article class
\usepackage[english]{babel}
\usepackage[utf8x]{inputenc}
\usepackage[protrusion=true,expansion=true]{microtype}
\usepackage{amsmath,amsfonts,amsthm} % Math packages
\usepackage{graphicx} % Enable pdflatex
\usepackage[svgnames]{xcolor} % Colors by their 'svgnames'
\usepackage{geometry}
\textheight=700px % Saving trees ;-)
\usepackage{url}
\frenchspacing % Better looking spacings after periods
\pagestyle{empty} % No pagenumbers/headers/footers
%%% Custom sectioning (sectsty package)
%%% ------------------------------------------------------------
\usepackage{sectsty}
\sectionfont{% % Change font of \section command
\usefont{OT1}{phv}{b}{n}% % bch-b-n: CharterBT-Bold font
\sectionrule{0pt}{0pt}{-5pt}{3pt}}
%%% Macros
%%% ------------------------------------------------------------
\newlength{\spacebox}
\settowidth{\spacebox}{8888888888} % Box to align text
\newcommand{\sepspace}{\vspace*{1em}} % Vertical space macro
\newcommand{\MyName}[1]{ % Name
\Huge \usefont{OT1}{phv}{b}{n} \hfill #1
\par \normalsize \normalfont}
\newcommand{\MySlogan}[1]{ % Slogan (optional)
\large \usefont{OT1}{phv}{m}{n}\hfill \textit{#1}
\par \normalsize \normalfont}
\newcommand{\NewPart}[1]{\section*{\uppercase{#1}}}
\newcommand{\PersonalEntry}[2]{
\noindent\hangindent=2em\hangafter=0 % Indentation
\parbox{\spacebox}{ % Box to align text
\textit{#1}} % Entry name (birth, address, etc.)
\hspace{1.5em} #2 \par} % Entry value
\newcommand{\SkillsEntry}[2]{ % Same as \PersonalEntry
\noindent\hangindent=2em\hangafter=0 % Indentation
\parbox{\spacebox}{ % Box to align text
\textit{#1}} % Entry name (birth, address, etc.)
\hspace{1.5em} #2 \par} % Entry value
\newcommand{\EducationEntry}[4]{
\noindent \textbf{#1} \hfill % Study
\colorbox{Black}{%
\parbox{6em}{%
\hfill\color{White}#2}} \par % Duration
\noindent \textit{#3} \par % School
\noindent\hangindent=2em\hangafter=0 \small #4 % Description
\normalsize \par}
\newcommand{\WorkEntry}[4]{ % Same as \EducationEntry
\noindent \textbf{#1} \hfill % Jobname
\colorbox{Black}{\color{White}#2} \par % Duration
\noindent \textit{#3} \par % Company
\noindent\hangindent=2em\hangafter=0 \small #4 % Description
\normalsize \par}
%%% Begin Document
%%% ------------------------------------------------------------
\begin{document}
% you can upload a photo and include it here...
%\begin{wrapfigure}{l}{0.5\textwidth}
% \vspace*{-2em}
% \includegraphics[width=0.15\textwidth]{photo}
%\end{wrapfigure}
\MyName{Your Name}
\MySlogan{Curriculum Vitae}
\sepspace
%%% Personal details
%%% ------------------------------------------------------------
\NewPart{Personal details}{}
\PersonalEntry{Birth}{January 1, 1980}
\PersonalEntry{Address}{111 First St, New York}
\PersonalEntry{Phone}{(123) 000-0000}
\PersonalEntry{Mail}{\url{me@home.com}}
\NewPart{Translated books}{}
\EducationEntry{"Maria Mitchel" (Women in Science) by "Dale Anderson" in Persian}{Aug 2015}
\sepspace
\EducationEntry{"Maria Mitchel" (Women in Science) by "Dale Anderson"}{Aug 2015} % in Persian
{in Persian3}{in Persian4}
\sepspace
\EducationEntry{"Maria Mitchel" (Women in Science)}{Aug 2015}%
{ by "Dale Anderson" in Persian}{}
\sepspace
\EducationEntry{Translating "Physics in minutes" by "Giles Sparrow" in Persian}{Apr 2018}
\sepspace
%%% Education
%%% ------------------------------------------------------------
\NewPart{Education}{}
\EducationEntry{MSc. Name of Education}{2010-2012}{Name of
University}{Descriptive text goes here. In order to maintain a stylish look, try to fill this description with a few lines of text. Do the same for the other entries in the education section.}
\sepspace
\EducationEntry{BSc. Name of Education}{2007-2010}{Name of University}{Descriptive text goes here. In order to maintain a stylish look, try to fill this description with a few lines of text. Do the same for the other entries in the education section.}
%\end{document}
with the result:

Please see the warnings (incompatible usage of\@ssect detected) about the usage of \usepackage{sectsty} ... If possible use another class for your cv.
\NewPart,\EducationEntryand\sepspaceare not defined. Presumably either because the package that defines them is missing or because a different\documentclassshould be used. Please make sure that the example exactly as posted here compiles for you and report all warnings and errors. TheOverfull \hboxmessage is not a fatal error (it is not even strictly speaking a warning), it means that some parts of your document are too large to fit into the space they were mean to go into. See https://tex.stackexchange.com/q/35/35864 – moewe Mar 18 '19 at 11:06