Level 3 challenge 11 nouns

I have still not got to understand when ‘ma’ ‘mein’ or ‘un’ is used before a noun. Would anyone be able to explain please

ma’ is short for mae which is the verb ‘is/are’ - i.e. the present tense of the verb ‘bod’, ‘to be’, for all pronouns except ‘they’. maen is the present tense of this verb for the pronoun ‘they’ (nhw).
Maen wouldn’t come before a noun, only before ‘nhw’. Mae would come before a noun when the noun is the subject of the sentence e.g. mae ci yn ddu.

Yn is one of those words that means different things depending where it comes in the sentence. When it comes before a noun, it probably means ‘in’ e.g. mae’r ci yn yr ardd.

Is that kind of what you’re after, or have I misunderstood? Could you perhaps give some examples of where these words are confusing you?