¿Cuál es la diferencia entre not comfortable y uncomfortable ?Puedes dar oraciones como ejemplo.

There isn’t actually a big difference. They are pretty much interchangeable. Uncomfortable is more common.
Ex.
“Is this comfortable for you?” “No it’s not comfortable.”
“Is this comfortable for you?” “No, it’s uncomfortable.”

“Do you want to sit here?” “No, this spot is uncomfortable”
“Do you want to sit here?” “No this spot is not comfortable”

“Uncomfortable” is more casual and more of a descriptive word.
“Not comfortable” is used more when something is originally expected to be comfortable. But again, they are interchangeable, and both uses are easy to understand to a native English speaker if you mix them up.

I hope this helps!