Assalamualaykum wa rahmatullahi wa barakatuh,
Alhamdulillah that you have started to memorise even if its the short surah.
Just to add a little.
If you want to memorise the bigger surah, try using only one Quran instead of a few mushaf. Repeat the ayat many times until you are confident enough to move to the next ayat. Lets say you have complete memorising the ayats for one page, then you should try to recite it continuosly from the first ayat of the page until the last. Then you can move to the next page.
What usually works for me is to memorise it early in the morning after I wake up from sleep. During that time, one's mind is fresh and whatever that comes in will easily be remembered. InshaAllaah.
I must say, it does takes a lot of determination to be able to memorise the Quran (esp for non-native arabic speaker). However, many hufaaz from around the world are non-arabic speaker. Istiqaamah is vital in memorising the Quran. InshaAllaah if you do it solely for Allaah's sake with Ikhlaas, you'll get much reward for it.
Listening to the audio of a good reciter is good too as that way you will know the correct 'pronunciation' of the huroof.
Wish you the best to memorise the beautiful Words of Allaah subhanahu wa taa'la by heart.
http://www.islamicbulletin.com/free_downloads/quran/quran_tajwid.pdf
Wassalam.