Can I say that "claim down" vs "cold down"?

[Polyester]

Clam down, you should not do that because you are free now.

Cold down, you should not do that because you are free now.

Which one is more common?

 

[tedmc]

Both are unheard of.
You probably mean "calm down" or "cool down".

not a teacher

 

[emsr2d2]

And your question should be "Which one is more common?"

 

[Polyester]

Calm down, you should not do that because you are free now.

Cool down, you should not do that because you are free now.

Which one is more common?

 

[tedmc]

Both phrasal verbs are common. They are used to tell somebody who is angry/agitated/disturbed/emotional/in a panic state/worried etc.
Used in the context of your sentences, they do sound a bit strange.

Who wrote those sentences or where did you get them from?

not a teacher

 

[Polyester]

I'm just making it by myself. Not copy from the other place.

 

[emsr2d2]

[STRIKE]I'm just making[/STRIKE] I just made [STRIKE]it[/STRIKE] them [STRIKE]by[/STRIKE] myself. [STRIKE]Not[/STRIKE] I didn't copy them from [STRIKE]the other place[/STRIKE] anywhere else.

See above. You need to practise writing complete grammatical sentences.

As tedmc said, both "Calm down" and "Cool down" are common but your original sentences don't sound very natural. We don't have any context in order to decide whether they might sound more natural in the right context.