The language is only part of it. In my opinion, you would learn even more about C by consuming well-known libraries written in C and trying to do something usef

The language is only part of it. In my opinion, you would learn even more about C by consuming well-known libraries written in C and trying to do something useful with it and complementing that with some books, etc rather than just learning the syntax and semantics of C. There are tons of useful/fun things you could do with C. Write some desktop apps with GTK, a web server with Mongoose (https://mongoose.ws https://mongoose.ws), etc.