Today I'm going to be helping you get the achievement Numero Uno for 20G. To complete this achievement you need to obtain first place in all competitive game types.
Below are the game types in which you need to win/come first:

• Land Race
  
• Air Race
  
• Sea Race
  
• GTA Race
  
• Rally Race - You must have 4 people in total
  
• Deathmatch - Can be done with 2 players
  
• Team Deathmatch - Can be done with 2 players
  
• Must complete all ten waves of a survival
  
• Gang attack
  
• Golf - Can be one hole
  
• Tennis - Can be set to one set
  
• Darts - Can be one set/one leg
  
• Arm Wrestling
  
• Parachuting - Must land in the target at the end otherwise it's an instant DNF
  
• Any challenge at the shooting range
  

You just need to win at one of each game type. These can be boosted with a friend and can be done within an hour of playing.

If your opponent/friend leaves early it won't count and you will need to complete the activity again.

The map I used for the Deathmatch/Team Deathmatch
Ace Liquor - Players: 2-6 - Area: Sandy Shores - Set the time limit to 10 minutes and set the target score to 10 kills.

I hope this helps. If you need any help please send me a PM and I will try and help as much as I can.