It takes 10,000 hours of practice singing to become an expert at singing. This time is excluding learning. It takes you singing a song 50 to 100 times before you truly master the song. After about 20 times you get most of the expression but you have to keep on singing to improve the last 10% not mastered. Part of mastering a song is being able to play the melody and sign alone while playing the melody on the keyboard, and also while playing the chords in the left hand. Expression is what your target is. Exaggerate the words. Change your vocal tone for each word.