Can a Christian believe in God but not believe in prayer? I'm a member of the church but I don't believe in prayer ? How do I overcome that?
Let's work backwards. You say you don't believe in prayer, yet the Bible says that Jesus taught, "Then He spoke a parable to them, that men always ought to pray and not lose heart" (Luke 18:1). To say you don't believe in prayer is to say you don't believe in Jesus' commands. After all Jesus said, "If you love Me, keep My commandments" (John 14:15). And that means you don't really believe in Jesus as Lord or the Bible. But then how can you claim to be a Christian, a follower of Christ? "But why do you call Me 'Lord, Lord,' and do not do the things which I say?" (Luke 6:46). And how can you claim to be a member of the church -- a citizen in Christ's kingdom?
The point is that you can't pick pieces of God's commands and say "I don't believe in that" without unraveling everything for which you think you stand.
The fact is that God said we must pray, he taught us how to pray, and he explained why we must pray. Either you trust God (believe Him) or you don't. "But without faith it is impossible to please Him, for he who comes to God must believe that He is, and that He is a rewarder of those who diligently seek Him" (Hebrews 11:6). Your problem is deeper than just not believing in prayer.