'Knowledge' in the Bible

This is why I suffer as I do. Still, I am not ashamed; for I know Him [and I am personally acquainted with Him] whom I have believed [with absolute trust and confidence in Him and in the truth of His deity], and I am persuaded [beyond any doubt] that He is able to guard that which I have entrusted to Him until that day [when I stand before Him].

always learning and listening to anybody who will teach them, but never able to come to the knowledge of the truth.

and how from childhood you have known the sacred writings (Hebrew Scriptures) which are able to give you the wisdom that leads to salvation through faith which is in Christ Jesus [surrendering your entire self to Him and having absolute confidence in His wisdom, power and goodness].