Are there any mistakes?

I just watched a documentary about a French politician. I found this documentary on the internet.
The documentary was more about the life of this young politician than his political ideas.

It depends on the person, but I find that kind of documentary interesting. (I wasn't really sure what you were trying to say with this sentence, but I did my best to change it into what I thought was right.)
Basically I like stories about people's lives, even though it's a quick summary of someone's journey.