How do i know if God is real?

well i dont know what to belive because how do i know that christanity is the right religion what if like someone else has it right and what if the bible has been changed to make goverments have more control with religion or what if aliens placed us all here because the genisis it says Let us make man in our image, in our likeness why does it say OUR i thought there was only one god? im really having some doubts and i have a feeling that im going to spend my whole life trying to figure out if god is real but im only 15 maybe i will understand with age