warning in admin after 5.0.1 install

This is just a warning, so it’s probably safe to ignore it.

To track down its source, attempt to disable all plugins, and use one of the default (Twenty*) themes. If the problem goes away, enable them one by one to identify the source of your troubles.

If you can install plugins, install “Health Check”: https://www.ads-software.com/plugins/health-check/ On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you, while you’re still logged in, without affecting normal visitors to your site. You can then use its admin bar menu to turn on/off plugins and themes one at a time.

See https://www.wpbeginner.com/plugins/how-to-deactivate-all-plugins-when-not-able-to-access-wp-admin/

hi,
there is no plugin for the moment and only twentyseventeen theme installed
could it be a 5.2 php error ?

>> 5.2 php error << Seriously? You’re on 5.2? That’s extremely old and insecure. Contact your host and get onto 7.2 ASAP.