Grammer check, for a short essay,

I have been tasked to write a short 300 word peice about a successful or unsucessful learning experience. Please would somebody be so kind as to have a look at what I have written and correct anything that is wrong gramatically. Your help is very greatly appreciated.

A successful learning experience for myself was during a course to become qualified as a Lifeguard. The group was being shown how to conduct CPR (Cardiopulmonary resuscitation) which is an emergency procedure which is attempted in an effort to return life to a person who has suffered a cardiac arrest. The procedure on how to do this was being demonstrated in front of the class, however my view was somewhat restricted due to the individual seated in front of me. Once the demonstration had been completed, I approached the trainer and asked for some help as my view had been obstructed and I was not certain of the correct techniques that I was required to use. The trainer then came over to the workstation I was using and asked me to adopt what I considered to be the correct position and demonstrate the technique that I thought was required. When I had finished my demonstration the trainer began to explain to me what I had done successfully and what I had done that was not quite as successful, he then adopted the correct position, whilst doing so explaining to me the reasons why each aspect was important and good ways to remember the positions should I ever be required to carry out this action in the future.

This was a positive and successful learning experience as the trainer took his time to explain and analyze in detail the different aspects of the action that I had either found difficult or had been doing wrong. By firstly getting me to demonstrate showed the trainer what I was doing correctly and also not doing correctly, he then did show and tell, where he again demonstrated for me to see what is correct whilst at the same time explaining the specific positions and the reasons for those positions.

Thanks Martin