I am looking for a cdrama with 

1) healthy relationship. no misunderstandings.

2) cute and fluffy 

3) have below 30 episodes

4) something that makes your heart flutter

5) no high school romance 

Once We Get Married

Professional Single

Assistant of Superstar

Dear Little Mermaid

Fall in love with a scientist

The Love Equations

Love me Like I do

Love me Love my Voice- this has 33 episodes butttt. literally it's the cutest thing ever. Such a healthy relationship, along with no breakups and annoying misunderstandings between the leads. So, I'd try it out if you haven't seen it. It also gives me Amidst a Snowstorm of Love vibes. So if you like one or the other, I'd try it. 

+1 Shanai Marriage Honey (this is an all-time favorite of mine & is worth mentioning even though it's a jdrama rather than a cdrama)

+1 Love Me, Love My Voice

+1 Amidst a Snowstorm of Love

I'd also add the following:

Forever and Ever (helps if you've seen One and Only, but that definitively DOESNT fit your vibes)

Hidden Love (this one has high school elements in the flashbacks, but it isn't really a high school drama)

Hi Venus

Marry Me!

Love O2O

The Oath of Love

There are other good ones if you're willing to watch more than 30 episodes