Yes, you are right. Maybe you do not exist. Maybe I am the only entity in existance, and all around me is a kind of simulation...
However, to assume all around me is not real I need to settle with some basic believes:
1. I exist in a physical form called 'human'
2. People around me are real and exists too
3. The world around me exists as I can perceive it (see, hear, smell, ...)
Without those basic assumptions there is no need to do anything. Just jump from a building, as nothing exists! However, if you do not believe other people are real, why responding to questions and comments in the first place in this Forum?