Swimming technique

Hi, started swimming 2-3 months ago and learned freeswim from youtube😅 Could really use some advice and help regarding my technique, also tips on how I in general can get faster and how i should continue to train (doing a full distance ironman in a year) Here is a video of 50 meters relatively relaxed pace ( a little slower than 1:20/100m) an easy 100 meters is usually around 1 1/2 minute, and i can maintain that for pretty long( untill i get pain in my shoulders😂)