documentclass[12pt,a4paper]{article}
usepackage{amsmath,amssymb,fancyhdr,url}
usepackage{graphicx}

usepackage{mathrsfs}
usepackage{tabularx,lipsum,environ,amsmath,amssymb}
%usepackage{algorithm2e}

usepackage[boxruled,linesnumbered]{algorithm2e}
usepackage{hyperref}% http://ctan.org/pkg/hyperref
usepackage{cleveref}% http://ctan.org/pkg/cleveref
crefname{Lemma}{Lemma}{Lemmas}
usepackage{booktabs}
usepackage{graphicx}
usepackage[table,xcdraw]{xcolor}
usepackage{tabularx,lipsum,environ,amsmath,amssymb}
usepackage{geometry}
usepackage{amsmath}

newtheorem{theorem}{Theorem}
newtheorem{definition}{Definition}
newtheorem{lemma}{Lemma}

begin{document}
section{Introduction}
begin{lemma}label{hh}
There exist a this and that to solve the problem
end{lemma}

The problem mentioned in the above text seems to be ~cref{hh} is very
end{document}