Is it legal to resell electronics outside the US without authorization from the manufacturer?

I am starting a business purchasing electronics such as iPads, iPhones, beats headphones, fitness trackers, computers, etc. I do this because while being an international student, I was always asked by friends to buy them these things and sell to them whenever I went home. Then they started asking me to ship them, so I decided to scale it to a legitimate business (I'm from Angola). Now I'm wondering if I open an online store and allow people to order apple products and products from other makers, won't I get sued by them? Here's the same question I asked on quora. Somehow the answer wasn't very conclusive, even the one I found on google. Does the first sale doctrine apply if I buy from a US company and sell overseas? If not, is there a way to do this legally. Btw, I looked up how to be an apple authorized reseller, and it will take years to meet the requirements, so I don't have a choice there.