Maru: Excuse me. Are you Seika-san?
Seika: Yes, I am. And you are? (lit. your name is?)
Maru: I'm Maru. Nice to meet you.
Seika: I'm Seika. Nice to meet you.
すみません is multi-purposeful. Mostly excuse me/I'm sorry...it's used when wanting to attract someone's attention or when apologizing. The さん Maru puts after Seika's name shows that they have just met and so is being polite - さん is a pretty neutral honorific, used for anyone on your same social level and safe for most people above and below your level.
The そうです is a common phrase meaning "yes, that's right" or "yes, it is". Adding ね(ne) on to it makes it one of the most common phrases in the Japanese language, an agreeing phrase like "mhm, i see" or "yes i agree with you" and is used almost constantly. XD You'll notice that later.
The おなまえは is made from the honorific O (to make it more polite) and namae (name) - the wa is the "topic marker", which will be covered in next lesson (yes, I promised this lesson, but well...) The full question would be おなまえはなんですか (What is your name?) The です is that equal sign I mentioned before, putting namae equal to nan (what). か is a question marker. The full question sounds...funny though. Japanese people have a tendency of trailing off their sentences, so leaving it at おなまえは？ is much more natural.
Maru: Sumimasen. Seika-san desu ka?
Seika: Hai, sou desu. O-namae wa?
Maru: Maru desu. Hajimemashite.
Seika: Seika desu. Hajimemashite.