They're is the contraction of they are.
Their indicates possession.
An apostrophe followed by an "s" shows possession in this sentence.
an, ana, ana, aan, a
An is used when the following word begins with a vowel.
The comparative suffix -er is used when the adjective is one syllable.
And if it ends in a consonant with a single vowel before it, you double the last letter before adding that -er on there.
The mistake is "your."
Your indicates possession by the person being addressed by the speaker. You're is a contraction of "you are."
More expensiveExpensiverExpensivestMost expensivest
More and most are never used with -er or -est.
They are mostly used when the adjective has two or more syllables.
Do is used when the subject is I, you, we, or they.
When the subject is he, she, or it, does is used.
Broke upbroke inbroke downbroke
Broke down means to fall apart, or collapse.
This post is translated from Spanish.