Some applications use escapeshellarg(), like Swiftmailer used in xenforo forum software
Also other needed functions are disabled.
We can’t enable these PHP functions on free hosting because of security issues. Just ignore this warning and continue with the installation.
Like the all caps text in the template says: this topic is for general website development discussions, not for InfinityFree specific issues. And the question “can you enable these functions on your server” is specific to us.