This translation from the American Bible Society makes this minor teaching more understandable:
2 Timothy 2:15 (Contemporary English Version)
Do your best to win God's approval as a worker who doesn't need to be ashamed and who teaches only the true message.
The second verse is far more meaningful.Here is a good translation with the important following verse added:
Ephesians 3:18-19 (New Living Translation)
18 And may you have the power to understand, as all God’s people should, how wide, how long, how high, and how deep his love is. 19 May you experience the love of Christ, though it is too great to understand fully. Then you will be made complete with all the fullness of life and power that comes from God. (this refers to receiving the baptism of the Holy Spirit)