You have to open the side menu, scroll down to Send Feedback, and choose Edit the map. After that, you can pick any road segment and suggest a new name, say the road is 1- or 2-way, tell it the road is closed, and so on.
See http://www.androidpolice.com/2017/05/04/map-maker-closed-road-segment-editing-available-users-google-maps/ 
With Map Maker closed, road segment editing is available to all users on Google Maps
Map Maker was completely shut down on April 2nd and at the time, Google promised that its features would find their way to the main Google Maps a… by Rita El Khoury in Applications, Google, News