Christianity has always had skeptics. To establish that Christianity is true, spend some time becoming familiar with common arguments against biblical doctrine. Some arguments are stronger than others.
Skeptics of Christianity often cite the so-called 'problem of evil' to indict Christians, and to indict God. How, they ask, could a loving God - or a supposedly loving follower - live a life with any joy, peace, or contentment while others suffer? Then, they ask, how could anyone be happy in Heaven when they know that others are suffering eternally in Hell? Consider this article as one example of how we might address such an objection.