There is a misconception here. We have to look at English complex sentences. A complex sentence has two parts. An independent clause and a dependent clause. There is a subject, verb, and object in the sentence as well. "Having achieved such a huge success, even changing the landscape of America, remembering why they started doing this business stopped being important to them." Let's break this In a complex sentence, the dependent clause usually goes first and then follows the independent clause. **Having achieved such a huge success,** [even changing the landscape of America,] @@remembering why they started doing this business stopped being important to them@@ The ones between the ** is the dependent clause. Without the independent clause right after, it would be useless. The information inside the [square brackets] is an additional piece of information that is independent from the whole sentence. The words between the @@ is the independent clause. This can be said as one sentence that doesn't need any of the information before it. However, it'll make more sense with the dependent clause. Now look at it this way: "Having achieved such a huge success, remembering why they started doing business stopped being important to them." An interpretation would be "the reason for doing business stopped being important because of the huge success that even changed the landscape of America." ---- As for the second one, it's just a standard complex sentence. "Smiling brightly" describes the man. It's a dependent clause. After the comma, we have "the man is a new comer". You are correct the man is the subject. However, smiling brightly modifies the sentence by adding additional information about the man who is a new comer. You can otherwise say it like this: "The man is a newcomer who is smiling brightly."