The material that you call “Advanced level” is what now is called “Old Course Level 3”, so it didn’t disappear – it was just renamed.
Here is a recent thread with some more info:
The other problem (with the login difficulty) seems to affect only users with iPhones. The app that you seem to use is largely outdated and it isn’t maintained anymore. If you search the App Store for “SaySomethingin”, you should find the newest version that is in active development.