I definitely believe in UFOs by the definition of the word, but that doesn't imply anything to be extraterrestrial, just that it's a flying object that's not been identified (yet).
As for extraterrestrial life, sure I believe that exists, the universe is vast and although the probability of life on a planet is low, there's an unimaginable amount of planets out there. Even though life forms of equal or higher intelligence than us may be even rarer, again there's an extreme amount of planets out there.
As for extraterrestrial life having visited our planet I have seen no convincing evidence. There's lots of videos and pictures out there, but mysteriously enough it seems everyone is walking around with a potato as a camera when they see something unusual. Besides, extraterrestrial life is subject to the same physical laws we are, long range space travel may very well simply be impossible. There's probably thousands of both organized and independent observatories around our planet, too many for any central power to shut down the publication of ground breaking observations.
I doubt we've been visited by extraterrestrial life all things considered, but there's obviously no way to prove we haven't, so I remain in a state of unknowing until there's conclusive evidence telling we have. What I've seen is too thin.