I concur with what Leaving_quietly said. I thought a few additional thoughts might be in order. As to their translation “Jehovah,” many comments have been made and many books and articles written. Here the Committee became stuck in the time warp of the early twenties when the name “Jehovah” was popular. In the mean time this name has gone out of vogue to be replaced by “Yahweh.”
What might assist you in your studies, is taking note of the style of NT writers. In this case, Paul quotes from a variety of verses in the OT. Verse 11 is a quote from Isaiah 28:16 (LXX → Greek Septuagint), which points to the Messiah. As has been pointed out, verse 13 is a quote from Joel (2:32 LXX), indicating YHWH. However, in our current copies of the LXX “lord” is used and not the Tetragrammaton.
If only the Committee stuck to their guns to only replace “lord” with the Tetragrammaton (= YHWH) at those places which are indicated as OT quotations. Unfortunately they decided to replace it in some instances where it is clearly not referring to the Tetragrammaton, e.g., the Lord’s day. Here the NT differentiates between the Lord’s (Jesus’) day, and the Lord’s (YHWH’s) day.