You can send mass e-mail messages under StaffCP -> Configuration -> E-mails. This would then go to everyone but would be a kind of "newsletter".
You can change the translation under the path - custom/languages/YOURLANGUAGE/general.php
If I am not wrong right now:
StaffCP -> Configuration -> API -> Enable API Verification: Disable
How can I activate the statistics "Average players" in the dashboard?
Like this https://prntscr.com/toh24
create your partner page with a custom page. Just go to your AdminCP then to Page, again to Page and then to create. If you have a banner from your partners you can add it by clicking on the image icon