Thanks to them you will gain additional experience points and money.
Each of them has its own goals that must be met to receive the reward.
1st Pony Express
Reward:
The questgiver is in the south-eastern part of the location.
After a short conversation, you’ll enter the car.
There is a point marked on the map that it’s crucial that you reach.
You have 4 minutes and 20 seconds to do so.
Watch out for opponents who will take a stab at destroy your car.
Take shortcuts, drive over ramps or go down the alleys to lose the pursuit.
When you get to the right point, jump out of the car and kill all enemies.
This completes the task - you will receive a reward.
@tcha
Reward: Depends on the rating.
This quest is available in the eastern part of the region.
Your mission is to go to the place indicated on the map and rate the Marshall Facility.
The lower the rating, the more opponents and the better the reward.
You just need to protect your rating by eliminating the enemies and surviving.
Monster Truck works well for this task.
Afterwards, you will be rewarded with money and XP.
2st Pony Express
The western part of the location hides another side activity.
This time, you’ll be driving across the desert all the way to the Rojas Desert North region.
There is a point marked on the map that you better reach.
You have 4 minutes and 20 seconds to do so.
Watch out for opponents who will attempt to destroy your car.
When you get to the right point, jump out of the car and kill all enemies.
This completes the mission and you will receive the reward.
3st Pony Express
This side activity is available in the western part of the location.
You will have access to a car that will take you to the northern part of Rojas Desert North.
You have 7 minutes to complete the task.

When you get to the right point, jump out of the car and kill all enemies.
This will end the mission - you will receive the reward.