You can permit a person to access your email folder in your Outlook on the Web. This article details how to share an email folder in Outlook on the Web.

This article details how to access another person's calendar in Microsoft 365 Outlook on the Web.

This article details how to share a calendar in Microsoft Outlook on the Web.  Only the calendar owner can share a calendar.  Any changes you make on the web will then appear in installed Outlook apps.