Have you seen a chimpanzee?(present perfect tense)

YESChimpanzees are great apes found across central and West Africa. Along with bonobos, they are our closest living relatives.

^_^ ❤

In this sentence, the word  this  is used as a determiner.
every time a pronoun stands next to a noun it denotes, it will be used as the determiner.
if you say: this is my mother, here  this  is used as a pronoun, because it isn't directly followed by a noun.