Yes, I believe in space aliens, and unlike others, no, I don’t believe they are “here” nor do I ever think they will ever be able to come here, nor us go there.
Space is so big, that given we’ve been emitting radio waves for over a hundred years, the radio “sphere” in space coming from us hardly encompasses very many stars at all. We live in a huge galaxy, one of billions of galaxies, and in our little corner of our galaxy our radio waves, traveling at the speed of light, haven’t even reached a significant portion of our own galaxy.
In the image below, you can see just how tiny an area that is, represented by the small blue circle, or dot.
That being the case, unless there are aliens that want to visit us and “hide among us” (for whatever reason), they’d really have to come from somewhere pretty close.
I don’t see it.
Regarding “UFOs,” aka unidentified objects in the sky, there are many natural phenomena that we don’t yet understand, but to take it there is something we have yet to identify and then extrapolate that it is some kind of alien spacecraft visiting across thousands of light years just to come here, is more than a stretch. It’s not science.