Questions & Answers about Ich toleriere den Lärm meines Mitbewohners nicht.
Why is it meines Mitbewohners with an -s at the end?
This is the genitive case, which shows possession (translating to 'my roommate's'). For masculine and neuter nouns in the genitive, the article gets an -es or -s ending (meines), and the noun itself also gets an -s or -es ending (Mitbewohners).
Why does nicht go at the very end of this sentence?
When you negate an entire action or verb (in this case, the act of tolerating), nicht usually goes at the end of the clause. If you were only negating a specific part, like the roommate, nicht would go right before that specific part.
Why is it den Lärm instead of der Lärm?
Lärm (noise) is a masculine noun. Because it is the direct object receiving the action of being tolerated, it must be in the accusative case, which changes the masculine article from der to den.
How does the verb tolerieren behave in the past tense?
tolerieren is a regular (weak) verb. Like most verbs ending in -ieren, it is a loanword. They conjugate regularly, but remember that in the perfect tense they do not take a ge- prefix. You would say ich habe toleriert, not getoleriert.