I have a question and I need answers so please help me

So I was talking to my guy friend about how my bf doesn't know when he's about to cum and my friend told me that his girlfriend has a implant shot that you take on the arm and you can't get pregnant it's called the contraceptive implant and before I get it he said it work that he cums in his gf all the time and she doesn't get pregnant but I'm still a little skeptical on google it says it's over 99.9% effective and my friend told me that he know a lot of people that use it and they not pregnant and it's a shot u take by the arm I just want to make sure if it does work cuz I need help and other opinions on wheatger I should get it or not because we both tired of condoms honestly. What do you guys think?