I think the real reason for the page not displaying are the last two lines. I deactived the zend.ze1_compatibility_mode in .htaccess and can see the setup page, now. I will ignore the chmod errors, as I think they only come up during setup and set data/ and backups/ to 777 as the setup suggested. I'm not sure if that's safe but I'm not making the rules on this server :-)
Thanks for your help, anyway
Thanks for your help, anyway