Dear Mr. Voller,
I am writing to inform you about the possibility of me not attending your evening culinary course.
I have recently interned at an international school as a full time job. As a result, I have to spend all day in my new work environment. A lot of work such as observing, making reports and planning for next lessons makes me always busy in the evenings. It is a best chance for me to study and gain experience in a professional work which can be valuable for my career prospects.
If available, I would like to temporarily stop this course and restart after three months when I finish internship time. Therefore, I sincerely appreciate it if you could understand my situation and send me the opportunity that I could register as soon as I complete my work.
I am looking forward to your response and continuing the course under your institution in the near future.
Yours faithfully. 
Dear Mr.  
Voller
,
I am writing to inform you about the possibility of me not attending your evening culinary course.
I have recently interned at an international school as a full time job.  
As a result
, I  
have to
 spend all day in my new work environment.  
A lot of
 work such as observing, making reports and planning for  
next
 lessons  
makes
 me always busy in the evenings. It is  
a
 best chance for me to study and gain experience in a professional work which can be valuable for my career prospects.
If available, I would like to  
temporarily
  stop
 this course and restart after three months when I finish internship time.  
Therefore
, I  
sincerely
 appreciate it if you could understand my situation and  
send
 me the opportunity that I could register as  
soon
 as I complete my work.
I am looking forward to your response and continuing the course under your institution in the near future.
Yours  
faithfully
.