CAE and CPE Writing training: Formal letter Sample and feedback

Hi again Gustavo,

I hope you are fine!
Could you please take a look at my letter? As always, I'll share and like!
Thank you again for your previous feedback, it has been really useful and even though I keep making mistakes I feel more confident now about my writing, because now I know what to do in order to improve. 
Thank you!

Writing task:

You recently attended a training course which was exceptionally good. Now you have decided to write a letter directly to the course leader. Say why the course was exceptional, why it was particularly suitable for you and how you are benefiting from it now.

Write your letter.

Feedback in red

Dear Diana, (Is Dear Diana formal enough?)

I attended the leadership course which took place in Barcelona University last June. I am writing to give you my impressions on such the course, which in my humble opinion, is one of the best courses I have had the pleasure to attend. of going to. (Not to use the word "attend" twice) // (You should mention what kind of course that was)

To be honest, I believed that it would fall short on my expectations, as I have previously attended been to other courses of similar nature not resulting to be quite what I had hoped for. However, I can undoubtedly say that this course was exceptional -the contents, the instructor and the methods were ideal to accomplish the goal of the course. Arguably, what I liked the most was the role play game activity, in which we had the opportunity to face a “real” situation, in which we could put in practise the mechanisms theory we had previously learnt. Not only it was htat fascinating, but also the instructor’s feedback. -Evaristo was exceptionally empathic and did know how to lead us to the right path.

As a matter of fact, I am currently using what I learnt in the course, in my job as a  project manager. I balance both work and studies, so I started applying some of your time-management techniques. No sooner had I started using them, than my partners perceived the sudden change. They say that I have improved my work.

Moreover, this leadership course is aimed at a labour environment, but it can also be applied in other aspects of life. Being an introvert person, I have always had trouble when having a conversation over the phone or even when having a face to face with any unknown person. However, after taking this course, I feel more comfortable in these daily situations and I am confident that my stress level has decreased significantly, improving therefore my life quality. (I would change the whole paragraph. Not clear what kind of course it was. You should clarify that in paragraph one)

I cannot thank you enough for organising this course. It has significantly helped me in many ways, and I am thankful for that. I hope you keep up the good work.

Yours faithfully, (Why so formal? You started the letter with Dear Diana, as if she was your friend)

Alicia