Which part of speech is 看起来: an adverb or a verb?
'看起来' means "seem" (look like) and it is a verb, same meaning as '似乎' (seem)


  https://www.merriam-webster.com/dictionary/seem
  
  seem:
  
  intransitive verb
  
  1 : to appear to the observation or understanding
  
  2 : to give the impression of being


Example:

He seems very weak = 他看起来很虚弱/ 他似乎很虚弱

he seems quite angry = 他看起来很生气/ 他似乎很生气

看起来 is usually reduced to 看来 in everyday speech