Can I write this way?

...unfortunately I didn't/haven't manage to check my
mail in the morning, that is why I could not come at 11:30.

In any case, I am very happy to pass this demanding exam. I believe
I have got the whole information that you could give me concerning
my essay, so I would not like to infringe on your time again.

I would like to thank you for the seminar. It gave us a clear idea
about essay structure and provided us with good examples. Moreover, it was a great opportunity to talk to you about our own difficulties and
get an individual support.