Finding the right definition of a word in the Greek

[Guido]

I have made notes on four verses in 1 Corinthians 1, not spending much time in doing so, and I may have written down some inaccurate interpretations of some or all of those verses. This is because I don't know the right definition to choose in the Strong's concordance. Based on some previous knowledge of mine, or just by guessing, I chose the definitions that made the most sense, and tried to phrase my notes reflecting my interpretation. The definition is often just one or two words in English. In the case of the words I chose "ambassador of the gospel" I did not get that from the concordance, I don't think, but simply wrote them down because I heard them used with respect to this passage before.

These are my notes so far, two of which I posted in another thread already, (which may have been corrected by others,)) I will just leave out the Bible verses themselves as I don't really feel like typing so much.

Notes on 1 Corinthians 1:1-4

1:1 The letter is from Paul and Sosthenes. God chose Paul to be an ambassador of the gospel, one belonging to Jesus Christ.

1:2 The letter is to the church of God at Corinth. The people in that church, and everyone who calls on the name of the Lord Jesus Christ everywhere, were made holy in the body of Christ and were invited to be saints. Christ is the Lord of all who call on His name everywhere, and the Lord of all in the church at Corinth, and the Lord of Paul, and of Sosthenes.

1:3 In this verse, Paul expressed his desire or prayer (I don't know which) that his intended audience would receive kindness and peace from God the Father and from the Lord Jesus Christ.

1:4 In this verse, Paul said that he always thanked his God, (the God whose Son is Jesus Christ, who is also God), because of those to whom he was writing, because of the loving-kindness of God given to them by means of Jesus Christ.

Please help me to understand how to choose the right Greek word definitions for words, so that I can study the Bible and interpret it with accuracy. Thank you.