Does it sound natural On Sunday we had Easter.
We went to a vigil service which started at 11 PM and finished at 4 am.
We made special.pastry and dyed boiled eggs in red.
I.put on weight since my pregnancy. I must shed more than ten kilos but I am afraid to go on a diet as it can reduce my breast milk.

Question

Does it sound natural On Sunday we had Easter.
We went to a vigil service which started at 11 PM and finished at 4 am. 
We made special.pastry and dyed boiled eggs in red. 
I.put on weight since my pregnancy. I must shed more than ten kilos but I am afraid to go on a  diet as it can reduce my breast milk.

Answer

It is fine.  You might also say "On Sunday, we celebrated Easter."

Happy Easter!  Christ is risen!

Answer

Well done. :)
It is not quite 100% natural though. I have made a few (small) corrections below.
You can say "Easter was on Sunday" or "On Sunday we celebrated Easter".
"We made a special pastry and dyed boiled eggs red." (no need to write "in")
" I have put on weight since my pregnancy" ("Have" for past tense)
"I must lose more than 10 kilos... " ("Lose" is the idiomatic word in English for decreasing weight)
"... could reduce ... "
Happy Easter! :)