I have created an email long years back in I guess year 2008 with ID say [email protected]
and some person has created a new email named [email protected] and now I am getting his emails on my gmail account.

I googled and found that gmail system ignores [.] in email ids and all emails having . will land to one email.

so hello.world - h.elloworld - hell.oworld etc will go to helloworld

my main concern is since I am receiving other person email on my gmail ID can this go vice-versa too?
like if someone sends an email to me at helloworld , can the other person with ID hello.world see my emails too?

It took me 10 seconds to find this:
https://support.google.com/mail/answer/7436150?hl=en