Hello!

I'm looking for nice school/sports/slice of life, the ones that are refreshing, similar to your typical sports/school anime.

The only drama I can think of is Weightlifting fairy.

if it's about sports, at least the male lead should be an athlete or something.

I'd like the charachters to be in high school or college.

It doesn't necessarily have to have sports in it, it can totally be a nice school-slice of life as long as it's not boring.

I prefer korean or japanese dramas, but I can watch chinese dramas as well.

To the Beautiful You -   kdrama
Buzzer Beat  -   Jdrama
Tumbling
Rookies
Yowakutemo katemasu
Nodame Cantabile

Taereung National Village is both sports and slice of life, but not school.  Although it kind of has that feel anyway, since they're athletes at a live-in training center.
My Mr. Mermaid is a chinese drama that is very good. It is about athletic swimmers. 
Project S The Series: Spike fits, but it's not SOL
Project S The Series: Side by Side
Pride (not in hs/college)
I second Tumbling
Sassy Go Go is great
Sassy Go Go is great
Age of Youth - it's about 5 college girls who all live together and sports isn't involved neither is school tbh but still watch it bc it is sooo good! I recommend it to everyone it's my fave lol
You would probably like Suikyuu Yankees! It's a high school drama about a boy's water polo team! If you know the sports anime Free! you'll see a lot of similarities between the two