Willing, voluntary, of one's own accord. Hekōn. Paul declared he preached the gospel willingly, not under compulsion. Obedience offered freely carries a weight that duty alone never can. Choose it.

to "practise", i.e. perform repeatedly or habitually (thus differing from G4160 (ποιέω), which properly refers to a single act); by implication, to execute, accomplish, etc.; specially, to collect (dues), fare (personally)

Wages, reward, pay. Misthos. Behold I am coming quickly and My reward is with Me. Following Jesus comes with a reward. Not payment for works but the gift of His presence forever.

To have, to hold, to possess. I have learned in whatever state I am to be content. Contentment is not about having more but appreciating what you have.

Stewardship, management, administration. Each one should use whatever gift he has received to serve others faithfully administering God's grace.

To believe, to trust, to have faith. Pisteuo. Believe in the Lord Jesus and you will be saved. Believing is more than intellectual agreement. It is a transfer of trust to Jesus.