In this code the letters are separated into two letter segments. Don’t worry about the end or beginning of words. Then each two-letter segment is reversed. Gift would be gi ft, then ig tf.
To decode the message, you re-reverse the letters and then read the message. Ig tf becomes gi ft. Just remember you don’t know where the words stop and start.
OH YW UO IF IN HS SI HW TA HT YE IW LL ER EM BM RE