QUESTION: How to set title of search results?

On my website www.lesliedegroot.nl the title of the search results is displayed as h1, but i would like to change it to h2, so it would look the same as the rest of the website.

How can i accomplish that?

You can override
components\com_search\views\search\tmpl\default.php

by putting copy

to:

templates\hot_flashes\html\com_search\search\default.php

then edit second one

I've tried this, but "templates\hot_flashes\html\com_search\search\default.php" does not exist.

I've got "templates/hot_flashes/html/mod_search/default.php" Do i have to overwrite that one?

Ok, you don't have it, so you put it there. That is called overriding so if file don't exist joomla default will be used. if you provide it then your will be used.