Can't install w/1and1

I’m using 1and1 (I know, it’s terrible, but I’m stuck with it now and trying to make it work) and I can’t get wordpress installed. I’ve added all the files to my directory, but when I go to the https://www.mywebsite.com/blog/wp-admin/install.php all it displays is the wp-config.php file and says this at the bottom:

Fatal error: Call to undefined function load_textdomain() in /homepages/19/d89342398/htdocs/blog/wp-admin/includes/admin.php on line 13

I’ve tried adding a .hcaccess.php file that says:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ./index .php [L]
</IfModule>

# END WordPress

but that doesn’t help either. Any suggestions?