Hi Burcu,
You will probably want to call your webhosting company and have them update the php.ini settings file for your website. It sounds like your webhosting company is not allowing your settings to work, because they control the global settings and have disabled your access to change them.
Nothing I do could fix your site unless you gave me root access to your webserver if you’re on a dedicated server. If it’s a shared hosting account, you will want to call the webhosting company.
Let me know if we can help, we’re always here if you need us and happy to check anything out that is a problem.
Ben