As others have already written, it takes time because your hand/eye coordination in the game is limited to your fingers or was previously through the pad. Now your body has to understand that you have to move... your feet have to learn to do what your fingers used to do. It takes a while, it helps a bit if you drive a lot anyway and have possibly moved many different cars. Because then the body knows how it has to work in principle.
Most players use their right foot for the accelerator and their left foot for the brake. This is usually not the case in normal road traffic, and something like this can also lead to problems.
I e.g. Since I drive a lot with a steering wheel in the game and have practiced a bit, I can brake my Cupra on the street with my left hand when I drive fast, which I would never have done before, and shifting using the paddle shifters is now much easier for me. So it also has advantages if you play with a steering wheel

.
Important with the steering wheel... do not use as much steering angle as with the PAD.. in the game when you use a pad you are often on the right or left stop and then simply let go of the stick again... if you drive the steering wheel like this , you lose control, or grip on the front wheels.
Give yourself some time, practice the licenses piece by piece and when you can drive them as fast as you can with the pad, go to the missions.
My other recommendation, especially at the beginning, is NOT to switch to the pad. Then take a break and try again later. Your muscle memory has to get used to it.
Once you get the hang of it, riding with a pad will seem totally weird/wrong.
Contrary to what others write, I am NOT in favor of immediately deactivating all assistants.
The countersteering assistant is indeed not a good tool when it comes to the feeling when driving. However, some cars are so disgusting to drive that he can't help flying off the track all the time.
But it is better to use cars that are very good on the road and can be controlled.
ASM is similar to Countersteer Assist, it can help keep cars that are difficult to drive on the road, but this is more important for vehicles that have poor/unstable handling.
I see the Tracktino control as a very useful tool and as a "safety net" I clearly recommend the use of TSC whenever you have the feeling that you are not safe enough with the car or if the car simply reacts too violently when accelerating.
As a "steering wheel beginner" who also has to get used to the pedals, it helps immensely AND in some situations it is faster than without TCS. If you can later accelerate almost error-free, then a deactivated TCS is undeniably faster.