Installation can't access tmp files

I am brand new to piwik!
When I started the installation procedure, I got the message:
problem writing temporary file ‘/var/www/vhosts/…/piwik/tmp/templates_c/wrt4d40690e684d5’ (my website is hosted by amen).
The access rigths of the tmp/templates_c directory are set to 755 and included files to 600. I cannot change this setting through my FTP access.
How can I hack the code to create the subdirectories under tmp with appropriate access rights to allow the installation procedure to work??
Thx

It cannot write that file. That means the directory doesn’t have sufficient rights to let it write. If you cannot change that you have to contact your hosting provider and ask them for a solution. Maybe they provide a separate Piwik installation that all customers can use. Frankly, as I hosting provider I wouldn’t allow people to run ressource hungry applications like Piwik on cheap virtual hosts. If a few more customers on that machine do it performance for all will go down heavily.