“Their travelling in there car”

They are travelling in their car

They + are = They’re ... “They’re” is a contraction of “they are” .

hence “They’re travelling there in their car”.

“There” is the opposite of “here” – it is an antonym. “There” describes a location or place or position.

“Their” is something which is possessive i.e. a group of people has something – that thing is “theirs”

And another thing: “eh walla, it worked!”

No.

It’s a phrase from a different language, known as French. The phrase is "et voilà" ...which loosely translates to something like “there you have it”.

Walla ... I ask you. Pronunciation of the French is something like “vwoller”, not “walla”.