Assuming you have an Exchange Online/Office 365 account configured in the mobile Outlook app, to move a message from the Junk folder to Inbox, either select the message or open it first, then hit the three dots menu in the top right corner > Move to folder.
As for general feedback on the Outlook app and its features, you can use the Feedback portal: https://feedbackportal.microsoft.com/feedback/forum/89a8afa3-2e1c-ec11-b6e7-0022481f8472