I am trying to create a game on unity, i have add several game objects and i wanted to make my player move. so i open up a C# script and started to type down a couple of if statements, though the IntelliSense in Visual Studio isn't showing nearly as much of the options that there should be and it states that there is no issues that have been found
So i decided to type down code that i knew wouldn't work 
Check that you have Visual Studio selected as the External Script Editor in Edit > Preferences....
Close Visual Studio if it's currently open.
Press the Regenerate project files button in the same view.
Open a script in Visual Studio by double-clicking it in the Project window.
If the issue ever happens again, redoing steps 3 to 5 should fix it.