Sein name
As a first name, that would be spelled the same.
You would say "su nombre"
The Name Alvaro means Guardian. To say the word Guardian in Spanish, you would say: Protector
"Ridge" if it is used a someone's name would be "Ridge" in Spanish. Using Spanish pronunciation, this would be "REED-heh".
The closest name to Edwin in Spanish would be Eduardo.
'I want to be with you' is 'Ich will mit dir sein' in German. It would be more romantic to say 'Ich will bei dir sein' which means 'I want to be near you'.
Is it a name? It would most probably be pronounced 'mahSAWchah' in Spanish
Sidny is a name. So in Spanish it would be the same "Sidny".
Karina is a person's name, and would remain the same in Spanish.
"What is your name?" is not the Spanish way of asking for that information. In Spanish, the common form of this question is "How do you call yourself?" or "How are you called?" You say it, "¿Cómo se llama?"
Nike is the name of a company, and it would not change in Spanish. For pronunciation, it would be NEE-keh