For example:
\documentclass[12pt,fromalign=right,refline=nodate,backaddress=false,addrfield=topaligned,foldmarks=false]{scrlttr2}
\setkomavar{signature}{Heime}
\setkomavar{fromaddress}{This and That}
\setkomavar{date}{January 2023}
\setkomavar{location}{\raggedleft\usekomavar{date}}% put the date into the
% location field
\setplength{locvpos}{\topmargin+1in+\headheight+\headsep+1.2\baselineskip}% move the location field
\setplength{firstheadwidth}{\textwidth}% limit the width of the head at the
% notepaper to the paper width
\setplength{toaddrhpos}{\oddsidemargin+1in}% possition of the recipient address
\setplength{toaddrvpos}{\topmargin+1in+\headheight+\headsep}
\setplength{refvpos}{\useplength{toaddrvpos}+\useplength{toaddrheight}}% possition of the reference line
\setplength{sigindent}{.5\textwidth}% possition of the signature
\let\raggedsignature=\raggedright
\usepackage{lipsum}
\begin{document}
\begin{letter}{Alice}
\opening{Something}
\lipsum[1]
\closing{Yours Sincerely,}
\end{letter}
\end{document}

For more information about using scrlttr2 (or package scrletter, e.g., in combination with class scrartcl) see chapters 4 and 21 in the KOMA-Script manuals and maybe also “How to create letters with KOMA-Script” (also available in German).
\usepackage[vscale=0.9]{geometry}? Or whatever proportion you want to use. – cfr Mar 05 '24 at 04:34letterclass. See Writing an official letter on how to write a letter using the defaultarticleclass. – Werner Mar 05 '24 at 06:27