Do I believe in aliens from outer space? Definitely yes.
Do I believe they have visited Earth, definitely no. Distances are far too vast for travel in either direction.
The idea that modern technologies were invented by visitors from space is really a silly idea because if you simply study where all these technologies came from you’ll see they gradually evolved from simple inventions to more complex inventions to the point we are at now. Just watch Modern Marvels if you don’t want to do an Internet search.