The PHP function "proc_open" and/or "proc_close" is not available

Hello
I try to run Contao manager on my web host but get the following error message.
PHP Web Process
The PHP function "proc_open" and/or "proc_close" is not available on the server.

Is this something I can fix myself or do I have to contact my web host?

My web host is ONE.com

With kind regards
Kennert

Maybe you can do this in the AdminPanel of your hosting environment. Otherwise, you would have to contact your hoster.