\documentclass[foldmarks=off,fromalign=right,backaddress=false,fromemail=false,fromurl=false,fromlogo=false,fromphone=true]{scrlttr2}
\usepackage[utf8]{inputenc}
\usepackage[slovak]{babel}
\renewcommand{\familydefault}{\sfdefault}
\title{}
\author{Stanislav Hoferek}
\date{\today}
\setkomavar{fromname}{Stanislav Hoferek}
\setkomavar{fromaddress}{ABC}
\setkomavar{fromphone}{0123456789}
\setkomavar{signature}{}
\setkomavar{subject}{}
\begin{document}
	\begin{letter}{Recipient}
		\opening{Dear ...,}

		\closing{Best regards,}
	\end{letter}
\end{document}