https://www.f4football.com/tutorial/advanced/players/gaining_experience

Hello.
One of my 6 coaches is like this
Basic Training Skills 20
Goalkeeper Training 60
Defense Training 67
Attack Training 98
Tactical Training 13
Resistance Training 60
Judging Players 25
Physiotherapy 22
The Physiotherapist has a 95 in physiotherapy, and is terrible in the others.
The scout too, only has 95 in the ability to judge players, and is terrible in the others.
What are these basic skills (SK) and what are they for?
I find it difficult to get a trainer above 90 in more than one skill, so I try to get the ones with the highest secondary skills, in addition to what he is good at, I believe it improves the average and training efficiency, right?
My CT is level 8, and it looks like this:
Training Efficiency
Basic Skills 33.62
Goalkeeper 67.13
defending 67.29
Forward 68.92
tactics 68.85
Resistance 42.30

It is very rare to see a staff with 90+ in physiotherapy or judging players and have a 90+ in another attribute too. Almost non-existent.
But there will be staff with 90+ in two of the coaching attributes, they pop up every now and then, but they are in very high demand so you will have to pay big wages to land them on your team.

Ideally, you should have 1 physio, 1 scout and 4 coaches all with a very high attribute in different departments, with 2 of the coaches having high attribute in multiple skills. This way you will have high efficiency in all training programs, high fitness recovery and accurate scouting. But it is easier said than done, so rotate your coaches and get the ones you need based on which skills of your players you are training. Always have a good physio (they are easy to get too), but you can sometimes let go of your scout and hire a 5th coach if you think you won't need your scout for sometime.

tutorial wrote :
There are 6 different training programs available to each of your players. The efficiency of these programs can be seen in your training page. The rate of improvement of your player in any attribute depends on the efficiency of the training program for that particular attribute.

Basic Skills : helps improve Passing and Heading
Goalkeeping : helps improve Handling and Reflexes
Defending : helps improve Tackling and Marking
Attacking : helps improve Shooting and Dribbling
Tactics : helps improve Positioning and Set Pieces
Endurance : helps improve Speed and Stamina

The best coach having expertise in each of the training programs automatically manages those, so make sure your coaches are good in each one of them to get good results. 50% of the efficiency also comes from your Training Centre level since you need the right equipments to train properly.