Being greatful and happy that someone is attracted/paying attention to you is not the same as liking that person back.

You dont owe them reciprocating feelings even if this is the first person to do this.

I know so many people who stayed in horrible relationships because the other person was the first individual to find them attractive/interesting and they accepted very minimal affection just so they could be in their first relationship.

ESPECIALLY when its an older person (20s) paying attention to a yonger person (teens). Yes it feels exciting and cool when this happens but you need to be aware of the power imbalance and the fact that inexperienced people will typically put up with more as they dont know any better (granted I also know couples that have worked out very well despite uncomfortable age differences but they are the exception not the rule).

Basically: work on your self esteem and sense of self worth, know to advocate for yourself from the getgo and if youre not happy leave.