Problem Details:

when I click on the app, it wont start. nothing appears. I try to redownload it but it missing some
files and it wont start.

Log Name: Application
Source: .NET Runtime
Date: 2/1/2019 6:57:02 AM
Event ID: 1026
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Computer: DESKTOP-8VACLTB
Description:
Application: osu!.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.AccessViolationException
at OpenTK.Platform.Windows.Wgl.CreateContext(IntPtr)
at OpenTK.Platform.Windows.WinGLContext+TemporaryContext..ctor(OpenTK.INativeWindow)
at OpenTK.Platform.Windows.WinGLContext..ctor(OpenTK.Graphics.GraphicsMode, OpenTK.Platform.Windows.WinWindowInfo, OpenTK.Graphics.IGraphicsContext, Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at OpenTK.Platform.Windows.WinFactory.CreateGLContext(OpenTK.Graphics.GraphicsMode, OpenTK.Platform.IWindowInfo, OpenTK.Graphics.IGraphicsContext, Boolean, Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at OpenTK.Graphics.GraphicsContext..ctor(OpenTK.Graphics.GraphicsMode, OpenTK.Platform.IWindowInfo, OpenTK.Graphics.IGraphicsContext, Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at #=zX6D6QxkrmLae6213Eg_KI9nJ0ivW.#=zjod0BK8=(Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at #=zGRACLtW51QfhNXz8YUqv9P4=.#=z0AeCnu9fmqWw(OpenTK.Graphics.GraphicsContextFlags)
at #=zGRACLtW51QfhNXz8YUqv9P4=.OnHandleCreated(System.EventArgs)
at #=zZcmpTEtszZUkVrAT5upgEaVjokhe.OnHandleCreated(System.EventArgs)
at System.Windows.Forms.Control.WmCreate(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.ScrollableControl.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Form.WmCreate(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Form.WndProc(System.Windows.Forms.Message ByRef)
at #=zV5AV41OBhkXH5DbR2HmjNZY=.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control+ControlNativeWindow.OnMessage(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control+ControlNativeWindow.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.NativeWindow.Callback(IntPtr, Int32, IntPtr, IntPtr)


Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name=".NET Runtime" />
<EventID Qualifiers="0">1026</EventID>
<Level>2</Level>
<Task>0</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2019-02-01T14:57:02.704229200Z" />
<EventRecordID>18305</EventRecordID>
<Channel>Application</Channel>
<Computer>DESKTOP-8VACLTB</Computer>
<Security />
</System>
<EventData>
<Data>Application: osu!.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.AccessViolationException
at OpenTK.Platform.Windows.Wgl.CreateContext(IntPtr)
at OpenTK.Platform.Windows.WinGLContext+TemporaryContext..ctor(OpenTK.INativeWindow)
at OpenTK.Platform.Windows.WinGLContext..ctor(OpenTK.Graphics.GraphicsMode, OpenTK.Platform.Windows.WinWindowInfo, OpenTK.Graphics.IGraphicsContext, Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at OpenTK.Platform.Windows.WinFactory.CreateGLContext(OpenTK.Graphics.GraphicsMode, OpenTK.Platform.IWindowInfo, OpenTK.Graphics.IGraphicsContext, Boolean, Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at OpenTK.Graphics.GraphicsContext..ctor(OpenTK.Graphics.GraphicsMode, OpenTK.Platform.IWindowInfo, OpenTK.Graphics.IGraphicsContext, Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at #=zX6D6QxkrmLae6213Eg_KI9nJ0ivW.#=zjod0BK8=(Int32, Int32, OpenTK.Graphics.GraphicsContextFlags)
at #=zGRACLtW51QfhNXz8YUqv9P4=.#=z0AeCnu9fmqWw(OpenTK.Graphics.GraphicsContextFlags)
at #=zGRACLtW51QfhNXz8YUqv9P4=.OnHandleCreated(System.EventArgs)
at #=zZcmpTEtszZUkVrAT5upgEaVjokhe.OnHandleCreated(System.EventArgs)
at System.Windows.Forms.Control.WmCreate(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.ScrollableControl.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Form.WmCreate(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Form.WndProc(System.Windows.Forms.Message ByRef)
at #=zV5AV41OBhkXH5DbR2HmjNZY=.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control+ControlNativeWindow.OnMessage(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.Control+ControlNativeWindow.WndProc(System.Windows.Forms.Message ByRef)
at System.Windows.Forms.NativeWindow.Callback(IntPtr, Int32, IntPtr, IntPtr)

</Data>
</EventData>
</Event>

osu! version: 20181231.2

Open your task manager and check to see if osu! appears in the list for a second after starting and then immediately disappears.

And try following this guide to check your event viewer for any crash logs and post anything you find.