You should be able to play this song in less than a week, if you can't, please play songs from level 1
The best way to learn this song, or any other song, is to watch the video at least 10 times. Concentrate on the movement of the keys on the piano first and then look at the actual notes on the staff, feel the music and try to sing along with it.
Once you are familiar with the song, and how it sounds, then print the music score PDF below.
Now, with the actual music sheet on your hands, play the video a few more times and put your eyes on the paper, and read along with the music, listen to the song while looking at the music sheet.
Do that a few more times and with your index finger, pointing at the notes as the same time as you are listening to the music.
Now, count the measures in the song, in this song This Old Man, you have 8 measures. And you have six days to play the song. If you see it like that, it's very simple, you just learn one measure per day, well two days you have to learn two measures, you see how simple it is. Look at the first measure, it only has 3 notes, Sol, Mi, Sol, I really think that you can learn that in a whole day correct?
