LETTER WRITING

Dear Iratxe,
How are you? I hope things are going well with you these days.
The reason I am writing is because I have finished my Almeria´s (I don't know what this is but you would not normally use the possessive here)  course and I wanted to know tell you that It had been it was a success.
I fell full felt happy with my work because the students who had made completed the course they had learnt enough. Nevertheless, the beginning was so hard that I was worried. I thought that I had failed at the first moment (Better would be to use "at the start" or a colloquial expression "at the first hurdle" ). Soon it changed (things improved), although the course wasn´t easy. When it finished I was very tired.
I know that you always want I me to tell you about my work, this is the reason of this mail. (You already said this at the beginning of the letter)  thank you for your interesting. I look forward moments for writing you soon. (It is not clear what you mean here, perhaps "I look forward to telling you more soon")
I hope to hear from you soon.
Love,
Elena

I use strikeouts and red words for correction of errors and I use green words for suggestions to improve the fluency of the text.

LETTER WRITING

Dear Iratxe,
How are you? I hope things are going well with you these days.
The reason I am writing is because I have finished my Almeria´s course and I wanted to know you that It had been a success.
I fell full with my work because the students, who had made (done??) the course, they had learnt enough. Nevertheless, the beginning was so hard that I was worried. I thought that I failed at the first moment. Soon it changed, although the course wasn´t easy. When it finished I was very tired.
I know that you always want I tell you about my work, this is the reason of this mail. Thank you for your interesting. I look forward moments for writing you soon.
I hope to hear from you soon
Love,
Elena

How are you? I hope you're doing well?
I am writing this letter to let you know; I successfully finished my Almeria's Course.
I was very happy with the result. The students did well. I was worried from the beginning, but it went well. The course was not easy. It took all my power. I am trying to keep update you about my work as you wished.
I hope to hear from you soon.
Love,
Elena