In this book, unless otherwise noted, the word "our" refers to Paul and Timothy (the one to whom this letter is written), as well as to all believers. (See: [[rc://en/ta/man/translate/figs-inclusive]])
"I, Paul, wrote this letter. I am an apostle." Your language may have a particular way of introducing the author of a letter. Immediately after introducing the writer, you may want to indicate to whom the letter was written, as in the UDB.
Here "our confidence" refers to the person in whom we have confidence. AT: "Christ Jesus, who is the one in whom we have confidence" or "Christ Jesus, whom we trust" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Paul speaks of his close relationship to Timothy as though they were father and son. This shows Paul's sincere love and approval of Timothy. It is also likely that Timothy was converted to Christ by Paul, and so this is why Paul considered him like his own child. AT: "who is truly like a son to me" (See: [[rc://en/ta/man/translate/figs-metaphor]])