No worries, there is no such thing as a stupid question!
You can find various announcements, news, and times for events (such as streams) in the Trove News and Announcements Forums. (Particularly the "News and Announcements" and "Patch Notes" sections.)
Unfortunately, the majority of announcements are fairly short notice. You can usually find out about streams and other events a day or so in advance though, as well as important news regarding the game and patch notes outlining what has been added/changed when a new update/patch is released.
All patches take place on Tuesdays, and the Developer streams where they answer questions, show sneak-peaks on upcoming content, and have giveaways, tend to take place every Friday at 12:20 PM PDT.
Aside from that, you can also usually find Stream Highlights posted within 1-2 days of the Friday stream on the General Discussion forums (essentially an outline of what was talked about - be sure to thank the author of said highlights if you read through them!) as well as Patch Notes Discussions (where you can see the patch notes and discuss/read about them further.)
Everyone else answered the rest of your questions regarding when the upcoming challenge changes/lunar lancer/shadow towers are being added (Tuesday, September 15th), so hopefully this additional information and link are of some use as well!