The meaning of the word believe is not what is being contested. It is your asserting that soil 2 had their sins forgiven and then fell away. When in fact the seed ---the word----fell on shallow soil and DID NOT TAKE ROOT deep enough to be anything real. It wasn't planted by the sower in the shallow soil, it fell into shallow soil. So if what you assert is true it should be no problem for you to prove that Jesus is saying a person can lose their salvation in that scripture. You would need to do it by finding all the passages where Jesus says you can lose your salvation.
I have shown you where He says we cannot. And let's apply a bit of logic to it also. Believing brings eternal life right? Is eternal life eternal or can it be removed, in which it was not eternal life. Was Jesus just kidding when He said "believe and you will have eternal life?"