Mono suddenly disappeared and Visual studio started to open instead. I tried to download from the off site, install xamarin studio, but all VS opens. In preferences, only browse and open the standard program for this extension is. I reinstalled the unit twice (when uninstalling, it says that it will delete all associated files, but when I reinstall and launch it, it immediately throws it to the project selection window with an already logged in account, as if nothing had happened)
Help please, VS, Xamarin, etc. do not suit me because of the startup time and after starting the computer just lies on its blades and hangs even in the browser, and there are no tips, so I had to freeze the project until I solved the problem

Answer 1, authority 100%

If the Unity version is 2018, then no surprise :

Starting with Unity 2018.1, Visual Studio will be shipped on Windows
2017 Community, MonoDevelop-Unity will no longer be supported.

Answer 2, authority 90%

Windows : Edit – & gt; Perferences … External Tools

Mac : Unity – & gt; Preferences … External Tools

Answer 3

Go to the top panel on the Edit tab & gt; & gt; Preferences … & gt; & gt; & gt; External Tools & gt; & gt; External Script Editor and change Visual Studio to MonoDevelop (easy boy!)