I have updated to 19.04 from 18.10 (which was updated to from 18.04 and maybe even 17.10 before that-don't remember exactly). Now the problem is that when I open Applications (either by Clicking it on dash or opening it using Super key) and then close it, the Applications overlay stays on and I am not able to open/switch to any other application. I have tried to switch to Wayland, but the only difference was, I was not able to fix this by restarting using alt+F2.
I solved this by disabling the "Workspace Grid" in gnome-shell. First I launched a terminal with Alt+Ctrl+t and then I issued the following command to open the gnome-shell extension preferences:
In the preferences I disabled the "Workspace Grid": See this picture
Lastly, I logged out and in again and the problem was gone.