sentance

I would offer a critique on your choice of tense as well:

"This is a challenging half-year for me" is in the present tense describing a six-month period (most of which probably has not yet occurred).  If you're describing the past six-month period, I would put this in past tense.  "This has been..."  If you're describing the current six-month period, I would suggest the future tense (because of what has not yet occurred).  "This will be..."

That will simply make the sentence more accurate.  To tighten it up at the end, I would offer the thought of removing the passive voice and rearranging slightly:

"...as my role and responsibilities have changed significantly."

"...as my role and responsibilities have been significantly changed.", otherwise, it looks good to me.