After module installation, updating translations still at 0%
After a few time doing something else, I went back to the issue. In fact a lot of JavaScript was not working correctly. 

Then I decided to go back to Configuration -> Performance and unchecked JavaScript aggregator and saved that configuration. See the image below :  



Now everything works fine!!! 

Now I can use admin toolbar's dropdown menu as well as coffee and all the other stuff is working well.

And thank you for reading me.