In Chinese (Mandarin) does the adjective come before or after the noun?

I assume you're talking about an attributive adjective? (one that is attached to the noun, like "the *big* dog runs")
They come before the noun, like they do in English :)
ie. 小狗 (xiao gou) = small dog (xiao = small, dog = gou)
負責任的人 (fu ze ren de ren) = Responsible person (fu ze ren = responsible, ren = person)

Predicative adjectives (one that comes in the predicate like "the dog is *big*") obviously come after in the predicate haha

either way, it's just like English :)

however, all descriptive phrases come before the noun they modify too.
Like in English you'd say "the person *who speaks Chinese*" but in Chinese you'd put the "who speaks Chinese" part before "person" and say
說中文的人 (shuo zhong wen de ren = literally "speaks Chinese *word that connects adjectives and nouns* person"), so just be aware of that :)

Well, give me seconds to think because I don’t know how to put a “adjective” come before or after the noun either.
Ok, done and examples as follows.
In Chinese, “This is a beautiful flower” we could say anyone one of the following three, all have the same meaning. And all three are
normal and nice
“這是(This is)一朵(a)漂亮(beautiful) 的(pronounced “di”) 花(flower)”
“這朵花(This flower)很(very)漂亮(beautiful)”
這朵花(This flower)漂亮(beautiful)的(di)很(very)
As you could see, and now I also see.
The first sentence do have a “verb(is:是)” and the adjective is before the noun, and we need to put “di” in between.
The second sentence, Holy moly, besides there is no “verb”, and “很” means very, seems needed. If you miss “很 ” , yes, it’s understandable, acceptable and correct , but it just seems not nice enough. While in the first sentence, to put or not put “很” before beautiful is not important. And, of course to put “很” means to emphasize. But in the second to put “很” before “beautiful” seems needed to have a function to end a sentence.
The third sentence “這朵花(This flower)漂亮(beautiful)的很”.
Now you and I both can see, adjective could be put before or after noun.
But how about “很”, I don’t know, may be, it’s an adjective, or may be, it’s an adverb for foreign people. For us we don’t know, we just know which sounds normal, which sound nice.
I am an English learner. I know how difficult it is to learn English.
But now I have a feeling, if you want to learn Chinese, that will be much difficult than my learning of English.