Concerning your statement that I am good teacher and wise ... It is following ...

II Cor. 4...... Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God;
6Who also hath made us able ministers of the new testament; not of the letter, but of the spirit: for the letter killeth, but the spirit giveth life.

God ordained for me to do this work ... Then HE taught me and still teaches me ... I just share what HE teaches me. 

Very simple.

Jesus said:  I can of mine own self do nothing: as I hear, I judge: and my judgment is just; because I seek not mine own will, but the will of the Father which hath sent me. Jn. 5:30

Paul said:  And I, brethren, when I came to you, came not with excellency of speech or of wisdom, declaring unto you the testimony of God. 2For I determined not to know any thing among you, save Jesus Christ, and him crucified. 3And I was with you in weakness, and in fear, and in much trembling. 4And my speech and my preaching was not with enticing words of man’s wisdom, but in demonstration of the Spirit and of power:  5That your faith should not stand in the wisdom of men, but in the power of God. I Cor. 2