> because it(Is this ok? What pronoun should I use for a name of companies?) caused a fire.

"they" might be more appropriate, referring to the people that operate and staff the company and were responsible for the fire.

Ran across this page a while ago, it covers mistakes made commonly even by native English speakers. Some of them are quite advanced. It can help anyone.
http://www.dumblittleman.com/2006/12/40-tips-to-improve-your-grammar-and.html