How to input a different player on the same level

help me please…
I have a car simulation game, with 1 circuit, and 3 different model car with different specification. can you help me make the menu selection.

before this, I made 4 scene

-main menu/car selection (with command Application.LoadLevel)

-car A with circuit

-car B with circuit

-car C with circuit

at begining of game selecting a car is fine, but everytime I pause and back to main menu and select another car, it just go freeze. can anyone help me?

Should CAR A + circuit be in quotations?

Also, you could just use one level and use PlayerPrefs to store which car they selected.

PlayerPrefs

thx for replies,
the quotations is my mistake, I rewrite them back in english for this forum, before I use object name with my country language for ease when I explain it in my class

@moghes, actually the problem already solved, it happens because when I play the 1st round and pause then back to main menu, the pause status is still active (using Time.timeScale = 0;) then when I play another round with a same or different car it got freeze which is actually a pause.

but yeah I still looking for a better way for selecting car.
@thraxST care to give link or tutorial? the unitydocs give me headache.