Is Malaysian food very similar to Cantonese, Chaozhou and Fujian cuisine in the south of China? Is there a place called Guam in Malaysia?

Not necessarily, because most people are Malays, so malaysian cuisine is still the mainstream. If you go to Kuala Lumpur and Johor Bahru, there will be more Chinese food. Among them, the Chinese in Kuala Lumpur and Ipoh are Cantonese-speaking, and the Chinese in Johor Bahru are mostly from Fujian.