Check with phpinfo() the values used for the variables post_max_size and upload_max_filesize. If your webserver is using suphp the settings made in .htaccess for php variables are getting ignored. Creating a php.ini file to set these values might not help much either as these settings will only be valid for the directory this php.ini file is located. Instead you should rather adjust the variables in ther server-wide php.ini file. Though it might depend on your hosting plan if you have access to the server-wide php.ini config. If in doubt, ask your webhoster support.

@iionly

It's what i did when adjusting .htaccess didn't work and everything on my site's working fine. 

Thanks for your help. I talked to my provider and realized that it doesn´t work on this webspace anyway... I´ll move to arvixe.com next month..