Professor Brain was experimenting to create waves that increase the brain power, but his experiments went horribly wrong (as always) and made every person DUMB.
Now they don't even know what to do in their daily lives. So he quickly makes an app where people can post their questions and get replies from YOU. Don't look surprised there is an app for literally anything these days.
Your job is to reply people the best you can in order to keep the balance of this planet. Just be cautious.
Don't populate the earth too much
Don't make the humans go extinct
Don't make them too sad
Don't make them too happy
See how simple this was. Now go on help those poor souls and don't forget to have fun!