At first I will provide a quick overview just in case for those who don't want to read the whole thing.
Some people just want a quick solution without the whole lifestory behind a simple game mechanic.
If you want to see a bigger breakdown of each and every single component, it will be later in the guide

DON'T USE PRESETS!

No seriously just don't.

They are broken and don't follow the games mechanic.
The main reason for pitstop faults is fatigue and the presets absolutely disregard this and don't take it into consideration.

So the key is this:

1.Car building is useless in this game
2. Gym training lowers your pitstop time (this is what you want)
3. Pitstop drills lower the chance of a mistake (not by much)

When creating your training schedule for the next month be ware of the fatigue your crew will have on race day. You can check this by clicking the "Cumulative" button in top right corner and then by hovering on race day in the calendar. If the fatigue jumps over 50% the chance of a mistake almost triples. Which is a huge deal. Make sure that on every Sunday (or Saturday sometimes) that number is under 50% and it will help you tremendously. Also note that changing engine parts between sessions adds little bit of fatigue. So if you go into a weekend with 49% you put yourself in danger of accidentally increasing you pistop mistake chances.
Of course you will still have some pitstop mistakes. 10% is still a lot but way better than over 30% every race. Given the fact, that you have two cars and sometimes even triple stops, it will be almost guaranteed, that your will have at least one pitstop mistake during the race.

Summary:
1. Don't use training presets. They absolutely suck
2. When setting up training schedule make sure your crew doesnt reach over 50% fatigue on race day. Check this by clicking "Cummulative" and hover over race day. If its over, just remove one training plan at a time to rest
3. Aptitude and Processes are most valuable skills for Sporting Director. Use the "Industry Standards" as the development focus for your Sporting Director
4. Never put any "Car Building" into your training schedule. It does absolutely nothing
5. Use the off season and pre-season to absolutely spam your training schedule. Remember. This pit crew is imaginary. They don't have families to spend their free time with

I'm not gonna go into numbers, because frankly I don't have the time for it, but I'll just provide a bigger breakdown for those, who are busy enough to find this themselves. I am just like you, but given the fact, that there is no guide, I decided to write one myself in hopes, that it will reach at least one person.

Here it goes!

Sporting director

Sporting director has 4 abilities
1. Training
2. Aptitude
3. Leadership
4. Processes

Let's break them down a little more

Training
It's the ability to efficiently develop the skill of team mechanics
Basically what this means is how much the crew improves during training and how less performance they lose between seasons. This can be a huge deal, because over time this can compound and snowball, if you are not careful.

Aptitude
The ability to help team mechanics reach their full potential
This is basically the ceilling that your crew can achieve. You can only improve so much until you hit a limit. Let's say your sporting director only has this at 70. That would roughly be a minimal time for pitstop of around 2.6 seconds. Your crew could try as much as they could, train as hard as they could but they could never breach the 2.6 second wall that this rating limits

Leadership
The ability to manage a team throug high-pressure situations
This single handedly lowers the chance of a mistake. That's all it does but it does it effectively. My director has it maxed out and my base mistkae % is always below 10%, which is really good.

Processes
The ability to develop and refine efficient workflows
This in my opinion is the most important skill to develop for your sporting director. All of the above are important, yes, but as I mentioned above fatigue is the biggest downfall of your crew. And this stat mitigates that. The higher this stat, the less fatigue your crew get from race weekends and training sessions. This is the gold mine for the delicious DHL Pitstop Award

Development focus

There are 5 ways of training your Sporting Director
1. Balanced
2. Communication Techniques
3. Drill Planning
4. Industry Standards
5. Innovation

Balanced
I have found this to be ineffective. Every Sporting Director has different stats and you need to work on specific parts. Avoid this at all cost in my opinion

Communication Techniques
This focuses on Aptitude and Leadership. This is not a bad thing to do, if your Sporting Director has a low skill ceilling in Aptitude and has a big chance of mistakes from Leadership

Drill Planning
This focuses on Training and Leadership. Honestly I think I haven't used this at all, because I usually go for something else. This would probably be last on my list of things to focus on

Industry Standards
This is the bread and butter on the road to the DHL Pit Stop Award. It focuses on the two most important skills. Aptitude and Processes. One is increasing skill ceilling and other is reaching the skill ceilling

Innovation
This focuses on Training and Processes. This is only one of two developments focuses that have Processes in it. Not a bad thing to got for, but Industry Standards is still better in my opinion

TL:DR
When it comes to development focus I usually go for Industry Standards first, because it gets the two most important stats (at least IMO) Aptitude and Processes. Then I go for Drill Planning that has the other two stats in it

This is where the magic happens. This is where your decision either help your crew become faster tha Guido himself (not gonna happen, Guido is the GOAT) or they will be just like Saubers pitcrew this year.
Enough of memes. Let's get to it.

There are 4 activities that you can do
1. Rest
2. Pit Stop Drill
3. Gym Training
4. Car Building

Rest
I think this speaks for itself. The crew do nothing and lower their fatigue.
This is really useful to do few days in a row before a race weekend. You gotta watch the fatigue level

Pit Stop Drill
There are 7 subcategories for this. This basically improves the teams ability to do each part of the pitstop. Raising car, removing tyres, putting new tyres on and releasing the jacks. These are good to do here and there. Especially if your sporting director doesnt really have a high "Training" stat. Then it can be a problem because your crew will lose stats between seasons. I always use balanced style for this, since you need every single stat anyway

Gym Training
Without a doubt the best and most important thing when it comes to crew training. This is what you want. This lowers the pitstop time. Over a season (with the proper sporting director) you can easily get this down to insane numbers. In just one season my crew is doing doing 2.1s pitstop with the ocassional 1.9s pitstops. If you do this, then you will easily get the DHL Pit Stop Award at the end of your first season.

Car Building
No clue what this does. Like honestly. Absolutely no clue.
Have ignored this in F1 Manager 22.
Have ignored this in F1 Manager 23.
Am ignoring this in F1 Manager 24.
Still don't see how this affects the game whatsoever.
If anybody has any clue about this let me know, because I have no idea what that even means.
I have all the achievemnts in 22 and 23. Hasnt affected me yet in any way. Don't see a point in stressing about this

Hopefully this guide has helped at least one person.
I remember struggling with this last year until I finally figured out how to do this.

So just watchout for fatigue
And ignore car building.

Like honestly....
I have no clue what car building does.....
WHAT DOES IT DOO????

I have ranted over Car building throughout this guide and thankfully comments came in to save the day.
Unfortunately its a good news and bad news kind of situation.
They found out and explained, that Car building attributes of the mechanics affects the time it takes to change parts during session and change setups/refills during quali and practice.
That was the good news.

The bad news is, this feature is even more useless than I imagined. Personally I dont run practice session at all. You can easily simulate them and still get close to 100% if you know what you are doing. And if few seconds between refills makes or breaks my whole quali runs, then my team sucks as a whole and not just this attribute.
Also AI suffers from this massively since they try to train/balance their mechanics attributes and then they have 2.7+ seconds pit stops. Which ruins the gameplay.

So as a player, feel free to ignore CAR BUILDING. It doesnt affect you in any significant way