Question: We know that matter exists and I have a question for you. Does antimatter exist? If it antimatter exists can it react with matter ?

Hi tibi!
very challenging questions this morning!
Yes, antimatter does exist, and yes, it reacts with matter, and we actually take advantage of these kind of reactions for medical purposes (for example the PET exam, to visualize things happening inside the body).
We call antimatter all those particles that have the same mass of our “standard” particles like protons, electrons, but have the opposite electrical charge. When an anti-particle encounters a normal matter particle, this lead to the so called “annihilation” of both (they sort of destroy each other), with consequent emission of high-energy photons, neutrinos, and other particle–antiparticle pairs. This can happen, for example, even in our atmosphere, due to the presence of cosmic rays!
I think this is more or less what I know about antimatter. There is surely much more, but you should better ask to a particle physicist! 😉