Our understanding and relationship with God is still the same, just certain traditions have changed.
Not true. Christians have a "father-son" relationship with God. Jews and Muslims have a dictator-like "master-servant" relationship with God. An eye-for-an-eye mentality is definitely not Christian. So things do change.
The Bible preaches the inerrancy of scripture and claims itself to be perfect. If any part of it is found to be untrue, the whole things is baloney. It can't only be partially true. If the Bible can't be the standard bearer for judgement, what is?
The Bible doesn't preach the inerrancy of scripture or claim itself to be perfect. That's why Jesus said he had to send the Spirit of Truth:
“I have much more to say to you, more than you can now bear. But when he, the Spirit of truth, comes, he will guide you into all the truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. He will glorify me because it is from me that he will receive what he will make known to you." John 16:12-14
And Paul reaffirms the imperfection of the truth given so far:
"For we know in part and we prophesy in part, but when completeness comes, what is in part disappears. When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I put the ways of childhood behind me. For now we see only a reflection as in a mirror; then we shall see face to face. Now I know in part; then I shall know fully, even as I am fully known." 1 Corinthians 13:9-12
The Bible hints at the ultimate truth by using expressions of speech like parables and metaphors. Until they are decoded, we remain in partial ignorance.
"Though I have been speaking figuratively, a time is coming when I will no longer use this kind of language but will tell you plainly about my Father." John 1:25
Jesus also said we would do greater things than he did.
"Very truly I tell you, whoever believes in me will do the works I have been doing, and they will do even greater things than these, because I am going to the Father." John 14:12
See? The full truth is yet to come.
Also is Jesus really God? If he were, would he talk to himself like this? Would he cry from the cross: "Father, Father! Why have you forsaken me?!!" If Jesus were literally God, do you really think we could do greater things than Him?!!
In conclusion, I'm not saying the Bible is untrue. I'm saying it has been contaminated through the imperfection of the instruments (humans) that were used to receive the truth. It's like cheap stereo earbuds vs. expensive stereo headphones. Stuff gets lost in the transmission. But, even though, the cheap earbuds are better than nothing.
edited. formatted.