Thanks everybody for the feedback.
I`ve encountered one issue, as well as multiple people, who have texted me about this. You can see the screenshot of this bug.
It occurs after some races that you can choose in "Quick Race" mode. Let`s say, that you`ve chosen 10 races on Bullseye Speedway with Qualification before each race and choose the distance of 40 km. The problem is that after second or third race, during loading screen, this window shows up. And because your script (next chapters of guide) clicks on Enter, you will go back to main menu, World Cup, 1 tournament and drive straight into the wall. It isn`t the awaited result, isn`t it?
I`m kinda new to the Unity Engine, so without source code, there`s not much I can do. That`s why, I`ve created the "ticket" with the name "Unique bug" about this bug - in the official Discord server of the game in "cs-bigs-issues-support". I hope, that developers will see and react to it and maybe provide some solutions to how this issue could be resolved. Yet I haven`t got any answer about the situation, maybe support team is just busy, I`ll wait. If you have encountered the same issue, leave the "purple worm" emoji on the post in the Discord, so support team can see, that lots of people have troubles with this bug.
You can still use the provided method, but remember, that at this moment, bug hasn`t been fixed, so you might encounter it too

Firstly, you need to install such software as "AutoHotkey". It gives you an option to write scripts for emulation of keyboard activity. Just past "AutoHotkey install" in the Google search-bar and you will see the official website of "AutoHotkey". In case, you cannot google it - "https ://www .
autohotkey .com" - remove the spaces and past it into your browser.

---

Okay, you`ve installed this software, great. Here comes another trick:
1). Create a new file with ".ahk" extension;
2). Open it using some text editor (Notepad, Word, WordPad);
3). Paste inside this code:
; Переменная для управления циклом
toggle := false

; Начать удерживать стрелку вверх и нажимать Enter каждые 10 секунд по нажатию L
L::
toggle := true
SetTimer, HoldUpKey, 1 ; Устанавливаем таймер для удерживания клавиши вверх каждые 1 мс
SetTimer, PressEnterKey, 10000 ; Устанавливаем таймер для нажатия клавиши Enter каждые 10 секунд
return

; Прекратить удерживание клавиш по нажатию K
K::
toggle := false
SetTimer, HoldUpKey, Off
SetTimer, PressEnterKey, Off
DllCall("keybd_event", "UInt", 0x26, "UInt", 0, "UInt", 2, "UInt", 0) ; Up up
DllCall("keybd_event", "UInt", 0x0D, "UInt", 0, "UInt", 2, "UInt", 0) ; Enter up
return

; Функция для удерживания стрелки вверх
HoldUpKey:
if (toggle)
{
DllCall("keybd_event", "UInt", 0x26, "UInt", 0, "UInt", 0, "UInt", 0) ; Up down
}
return

; Функция для нажатия Enter каждые 10 секунд
PressEnterKey:
if (toggle)
{
DllCall("keybd_event", "UInt", 0x0D, "UInt", 0, "UInt", 0, "UInt", 0) ; Enter down
Sleep, 50 ; Задержка для симуляции удерживания
DllCall("keybd_event", "UInt", 0x0D, "UInt", 0, "UInt", 2, "UInt", 0) ; Enter up
}
return

4). Russian words are just comments for the code. It works this way: when you touch the "L" key, "ArrowUp" will be activated every milisecond and "Enter" will be activated every 10 seconds; when you touch the "K" key, script stops working. Activation of "Enter" is needed to confirm start of the next race.
WARNING: Using "L" or "K", while script is active in "Task Manager", may trigger the script activation. After you are finished with farming, open "Task Manager" with Ctrl+Alt+Delete and terminate "AutoHotkey" process.
5). Save and close your ".ahk" file.

Click twice on your script. Launch the game. Open "Free Play" mode. Choose 10races, 12 RACERS, qualification each race, length of qualification in km, choose 40 km, same for the race - 40 km. In the very last section like tires and fuel, set everything to 0%, except for draft - set it to 100%. Don`t forget to choose "Prevent Lapping Collisions". For all 10 races - choose "Bullseye Speedway". Launch the race. Tap "L". Enjoy, your game will play itself for another ~400 minutes and you`ll get around 800km added to the counter. The best way is to launch the script and races when you go to sleep or to work. This achievement will still take a quite some time, but at least you don`t have to farm these kilometres manually. That`s it.

---

So it`s the end of this guide. Leave comment, if you have some problem with using this method and leave a thumbs up, if everything is working good. If you feeling extremely generous, you can help me with multiplayer achievements. Good luck and take care, Superstars:3