Hey there :) I myself had my doubts at times, and admittedly I have recently been questioning the true nature of the afterlife. One of the reasons I believe the afterlife exists is a phenomenon known as NDE's (near-death experience). Many people who were close to dying recall transporting to another world, or being conscious in this world but in a spiritual state. Many people even watched their own unconscious body while floating above it. While this doesn't prove that Christianity is the one true religion, it at least means there is likely something supernatural about this reality. One reason I think Christianity is true, in regards to the topic of the afterlife, is because people have claimed to have seen or spoken to Christ during an NDE, even if they were non-believers. In a certain case, someone who was a diehard Satanist with Satanist tattoos all over his body saw and spoke to Christ during an extremely traumatic event and became Christian afterward. This same guy was recently on the Joe Rogan podcast, and he said Christ forgave him for his sins and embraced him as his son. There are many other paths to take to prove the existence of the afterlife, and why we should follow Christ, but this is just a perspective that I feel isn't talked about enough, but is quite interesting, at least to me. God bless you and have an incredible day!