Hi Martin Webber,
You can easily highlight texts in latex using different packages. Especially for highlighting texts, you can either use "soul" or "xcolor". Once you have used these packages, you can use the "\hl{}" command to highlight the texts that you wish. Kindly, note that in the command "\hl", both "h" and "l" are small letters. For example, you can use a code like this: \documentclass{article}
\usepackage{color,soul}
\begin{document}
\hl{My Document}\\
\textbf{Lorem Ipsum} dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.\\
\end{document} If you are facing difficulties in compiling documents in LaTeX, I would suggest you to use this guide (https://typeset.io/resources/learn-latex-beginners-step-by-step-guide/) while typesetting your documents. Or else, just drop your question here and I will be happy to offer any help that I could.