The bible is not hard to understand in the things we need to know to faithfully serve God, to worship him, and to be saved!
Yes, there are some things that are "difficult to understand". 2 Peter 3:16 indicates that.
Why are those things hard? Partly because the Bible tries to describe spiritual things to firstly beings.
But also, in that verse, they are difficult to understand because men twist and distort the words!
Some twist the words, because they want to hear a word that matches their own desires. (2 Timothy 4:3-4). They are not diligently studying the word and correctly handling the word! (2 Timothy 2:15)
Some simply listen to what someone tells them about the Bible and do not search the scriptures daily to see if it is true! (Acts 17:11)
This all leads to confusion! The Bible, however, says, "For God is not the author (source) of confusion." (1 Cor 14:33). When there is confusion, it is not God's fault; it foes not come from God! It comes from men and it comes from the devil.
For example, God told Adam and Eve that if they ate from the forbidden tree, they would die. The devil told them, "You shall not surely die.". (Genesis 3)
When God gave his word, Adam and Eve understood what God said. They even repeated it!
But the Satan told them something different, and appealed to their desires. No longer listening to only what God said, they followed something else.
Did God know confusion would cause problems? Of course He did! That is why he gave us all of these passages (and more) to warn about it!
But consider this.
For the most part, there is no confusion concerning many of the things the Bible says.
As for certain facts, places, names, and many details; it would be difficult to find confusion. People know the Bible teaches Jesus was born in Bethlehem, died on a cross, selected apostles, performed miracles, etc. People know the Bible teaches Adam was the first man, Noah survived the flood in an ark, Moses received the 10 Commandments on Mount Sinai, and many other things taught.
The only place they have difficulty is in what the Bible teaches in the way of commands. Why? Because some do not wish to obey those instructions!
For example, Jesus Said, "He that believes and is baptized shall be saved." (Mark 16:16)
That is a simple statement! You would have to have help to not understand that! Yet, there is a lot of confusion concerning it!
Some say, "He that believes and is baptized shall be saved."
Some say, "He that believes is saved and shall (later) be baptized."
Some say, "He that is baptized (as an infant) is saved and shall (later as he matures) believe.
All three of those are not what Jesus said!
What would Jesus have said if he had meant, "He that believes and is baptized shall be saved"?
I believe he said what he meant, and meant what he said!
But, the many different views and teachings from men have caused confusion on this matter!
To correct this, we simply need to return to what the Bible actually says!
We need to change our views based on what the Bible teaches, rather than trying to change the Bible to fit our views and desires!