I believe they exist, they must! earth is too small compared to the vastness of the universe you know? But look at us! we are full of life, when i was a kid i watched this documentary of an old white grandma who lived in Africa and claimed she had fell in love with an alien and gave birth to a half alien child. she said they have more advanced technologies than us they use light propulsion to travel, she said they live in the nearby solar system called Alpha Centauri start system. I was pretty convinced as a kid hahaha, my inner child still hopes it's true! Also watching the movie Arrival (Very good movie if you love aliens) made me want good aliens to come find and be friends :)