I have a multipage document that has a larger header on the first page. However, it is not a titlepage, I don't know where it ends. I would like the pagebreaks to be determined automatically. This is almost solving my problem. For a better view I would like to shift downwards the header on the first page a little. This means also the textheight is decreased for this page. But by increasing the top parameter the textheight isn't adjusted and the footer disappears from the page. There are quite some questions on this issue but I just can't find the one solving my problem. Here is my code so far.
Many thanks.
\documentclass[11pt,a4paper]{article}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[showframe,left=25mm,right=25mm,bottom=25mm,top=32mm,headheight=14.0pt]{geometry}
\usepackage{fancyhdr}
\usepackage{lipsum}
\pagestyle{fancy}
\fancyhead[C]{all but 1st page}
\fancyfoot[L]{leftfooter}
\fancyfoot[R]{rightfooter}
\fancypagestyle{firstpage}
{
\newgeometry{left=25mm,right=25mm,bottom=25mm,top=32mm,headheight=66.0pt}
\chead{1st page\\1st page\\1st page\\1st page\\1st page}
\lfoot{leftfooter}
\rfoot{rightfooter}
}
\begin{document}
\thispagestyle{firstpage}
\lipsum[1-15]
\end{document}

\newgeometrystarts a new page. My code uses the same parameters for the page as all other pages, but neutralises the warning message about headheight, just smashing the header content. How much it goes under the header base line depends on the argument given to\raisebox. You can have some empty lines at the beginning of the first page, and it won't matter if the header overflows into these empty lines – Bernard Jun 12 '19 at 17:41