Put a call on hold in Microsoft Teams
Source: https://support.microsoft.com/en-us/office
On Desktop
To place a call on hold, click More actions 
in your call window and select Hold.
Everyone in the call will be notified that they've been put on hold, and you can continue your call by clicking Resume.
People on hold (including you) won't be able to see or hear anyone else on the call. Screen sharing is temporarily suspended, too. Everything will return to normal once you resume your call.
Note: The maximum number of calls you are able to put on hold is limited to five at a time, with one active.
On Mobile
To place a call or meeting on hold, tap More options Select to see more options in your call window and select the hold option. To continue the call, tap Resume.