Chinese is the widest spoken language....not

 No. That would be like saying Indo European is one language.

It’s the most widely spoken mother tongue on the planet, with more than a billion speakers. But much of what people think they know about the Chinese language is wrong!
The biggest misconception is, of course, the idea that it’s only one language.
Linguists disagree on the exact dividing line between a language and a dialect. But what we call Chinese consists of between seven and 13 dialects (depending on the classification system), many of which are mutually imcomprehensible. Most Western linguists now call it a family of languages, rather than a single tongue.

which is why Chinese movies here have...Chinese subtitles.
The Chinese diaspora usually speaks Cantonese, but the Chinese government types speak Mandarin...
more at this article about Seven misconceptions about China and the Chinese language.

his language family.
1) The two main varieties are Mandarin and Cantonese.
When we refer to Chinese, we’re often talking about Mandarin. A staggering 850 million people speak it as a first language. But the second most commonly spoken variant is Wu Chinese with 90 million speakers. This is followed by Min and Cantonese (both with around 70 million).

 yet even Mandarin has quite a few dialects which are not the same.

 The standard Mandarin of Mainland China is based on the Beijing dialect, which is spoken in Beijing and the Beijing region. Almost every city in China has its own variation on standard Mandarin, and each of these could qualify as a Mandarin dialect.

the closest example of an English dialect is...Frisian.