"LIFTED" = hupsoo, "to exalt, elevate, set on high." This word is found in 6 N.T. locations (2 here):

In our present text, there is not only a specific reference to Jesus' crucifixion (seen in His comparison to the serpent lifted up on the staff), but also to a deeper meaning beyond the Cross. The Cross alone does not save; He must also be raised up from the grave. Belief in this is essential to one's salvation ( Rom.10:10). But it does not stop there. He must be lifted up from the earth, back into Heaven that He might:
(1)  Reign with the Father,
(2)  Become our Advocate with the Father,
(3)  Send the Paraclete (Holy Spirit -- a stand alongside) from the Father, and
(4)  Return in His Glory!

Man's best words I have ever heard or read depicting Christ and the serpent on the Cross is seen in Charles Spurgeon's Sermon #1,500.
It is the one outstanding recommendation I will make to the reader to obtain and enjoy.

"BELIEVETH" = pisteuo, "adhere to, trust, rely on."
Compare this word to 3:36: apeitheo, which means "to be unpersuaded."
Examine King Agrippa's word spoken to Paul concerning this persuasion: "almost thou persuadest [pietheo] me to be a Christian."

"EVIL" = poneros, "the evil or depraved nature in all mankind."

"DOETH" = poieo, "to do."
"EVIL" = phaulos, "worthless," or "that which stems from the depraved nature, paltry, ugly, poor, referring to a dull senseless viciousness."

NOTICE:
the difference between the "evil" of vs.19 and that found in vs.20 -- the former referring to the status of all mankind, and the latter, the end result as it is acted upon in any individual.

"DOETH" = same as above.
"TRUTH" = aletheia, simply, "Truth."
The emphasis here is on the one who practices the one or the other -- Evil or Truth. One who practices doing the truth, whose life is lived with a desire to do right, a "right-oughtness," this one will come to the Light and will not speak evil of it, nor be seen in resistance to it. (As illustrated with Nicodemus coming to Jesus.) On the other hand, one who loves evil -- that is one whose pleasure is in deriving pleasure from evil -- this one will shun the Light and make it his life's duty to blaspheme good (speak out or align against it). Their intent is not only to do evil, but to viciously attack all goodness that surrounds them. (None of us have to go far to witness this in today's liberal amoral society.)
Jesus says: "I am the Truth, the Way, and the Life, No man comes to the Father but by Me." Therefore, He is the Light to whom all must go for Eternal Life. The basis, then, for the ultimate rejection of Jesus can be seen in 3 successive aspects (or steps) of evil:

Here, Jesus is saying: All men are born with a depraved nature and live in spiritual darkness, but without acquiring Godliness, an acquired love for Godlessness will follow. What remains, as the love for evil (remember the words: "...the love of money is the root of all evil") continues to run its course through the soul of man, is an eventual development of an extreme hatred of all goodness. This person (or society) will viciously attack anything that resembles Godliness. They have reached the point of imminent judgment. This, Jesus warned the hardhearted Pharisees of on more than one occasion, and its example can be seen throughout the pages of the Old Testament (and secular history) with individuals and nations. Its truth remains relevant today. Witness the struggle of opposing forces in our culture today. But know this: God is Sovereign whether modern man of any age admits it or not, and no degree of darkness or Godlessness can or will extinguish His Light. He and it will prevail! (Draw your own conclusions here.)

So, what is the lesson for us here?

  Guard your heart,
  Be careful what you love, (for you may never know where it will lead.)
  And, love only Truth!

And, when encountering darkness, to any degree, do not engage it for battle or debate. Simply, do as He says: Let you Light shine...!
And the Father, who is in Heaven, will be glorified, as Jesus predicts.