Hello,
Some people seem to have many problems with Geometry Dash, mainly sounds not working or game not launching when pressing play.
I am here to try to address these problems with simple solutions!
NOTE: I have windows so all these fixes are based on windows operating system.

This is a very common problem, happens especially to people who have enjoyed this game for a while.

When I press play, absolutely nothing happens:
If you press play, and nothing happens, steam shows that you are playing for 3 seconds and the returns to normal state. No error message, nothing.
This is most likely a problem with your save file. Here's how to fix this!

1. Enable hidden folders (AppData folder is hidden)

• Open control panel
  
• Search for "folder"
  
• Open folder settings/options page
  
• Go to "show" tab
  
• Scroll down until you see "Hidden files and folders"
  
• Make sure "Show hidden files and folders" is enabled

2. Locate C:\Users\Your name\AppData\Local\GeometryDash
3. Backup and delete CCGameManager.dat and CCGameManager.dat.bak
4. Open game
5. Load older saves from cloud

When I press play, game crashes and "Geometry Dash has stopped working" pops up!
This is likely caused by faulty drivers or corrupted game files.
Possible fixes:

1. Reinstall Geometry Dash
2. Go to C:\Program Files (x86)\Steam\steamapps\common\Geometry Dash\_CommonRedist\vcredist and install all the files in folders "2010" and "2013".
3. Update your graphics card drivers (or if they are up to date try downgrading them)
4. Update your windows
5. Delete some random folders and files inside Geometry Dash directory, like "fonts"
6. Put "-windowed" in steam start options
7. Wait for update 2.1

Custom music doesn't download/work
This depends on your computer/hardware.

1. Enable hidden folders (AppData folder is hidden)

• Open control panel
  
• Search for "folder"
  
• Open folder settings/options page
  
• Go to "show" tab
  
• Scroll down until you see "Hidden files and folders"
  
• Make sure "Show hidden files and folders" is enabled

2. Locate C:\Users\Your name\AppData\Local\GeometryDash
3. For any sound file, open it/check properties & file size.
4. If sound files exist but they are empty, there is a bug in your game where the game creates empty files whilst downloading music from newgrounds.

In this case:
1. Check your firewall
2. Update/downgrade your internet drivers
3. Try option "change custom songs location"
4. Wait for update 2.1

My game is in slow motion :O
This happens especially when you are recording or doing some heavy activity in background.

1. Go to ingame graphics settings
2. Press gear icon in upper right corner
3. Disable "Smooth fix"

I have screen tearing D:
This occurs when the game renders more frames than your monitor can handle. Screen tearing is different from lag.
If you are on windowed mode:

1. Go to ingame graphics settings
2. Press gear icon in upper right corner
3. Make sure vsync option is not checked

If you are on fullscreen:

1. Go to ingame graphics settings
2. Press gear icon in upper right corner
3. Make sure vsync option is checked


I hope these might solve your problems! If you have any friends who have these problems link this post to them :)