How are u? - aap kaisey hain ?(with repect) and with frnds and younger than you - tum kaisey ho ?
how = kaisey. You = tum or Aap. " are " can't be defined as a single word in hindi.
How old are u ???(explain what is old)
Aap ka umar kya hai ? or Aap kitney saal ke ho ? old means - purana but not used in sentence while asking this question.
What´s your name ? (explain what is your , is and name)
aapka naam kya hai ? your = aapka or tumhara & is = hai & name = naam.
Where are u from??? ( explain what is where and from)
aap/tum kahan se ho ? where = kahan & from = se.