***** NOT A TEACHER / ONLY MY OPINION
(1) Maybe something like:
Thank you so much for the beautiful flowers. They have really
cheered me up.
P. S. I most respectfully and gently suggest that you avoid
words like "for sending." You have the flowers, so -- of course --
they were sent (or brought) to you. Writing teachers tell us to
cut out all unnecessary words.
- For Teachers