"Where is the car key?"

Translation: 車のカギはどこですか？

[Helenzie]

Kagi is in katekana? Is it from another language?

[Yuzuling]

It's a native Japanese word and it has a kanji 鍵 but it's complicated so for emphasis it's sometimes written in katakana. You will see it both ways in Japan.

[RaphaelBar819848]

確に that kanji is tough to learn. RPG Maker games helped me a lot though.

[FlayflayCa]

車のカギわどこ? wasnt accepted. It just gets more and more strict the further you progress

[V2Blast]

The particle needs to be written は, not わ. Even so, your sentence seems overly casual.