I've been running consistently this week, and 8 p.m. is the best time for me to run. I've been running consistently this week, and 8 p.m. is the best time for me to run.

You could also say "I've been running consistently this week at 8 PM."

But today I (learned/just found out) that there's a quiz next Monday. But today I (learned/just found out) that there's a quiz next Monday.

I usually spend a whole week preparing for it, so this requires meI need to complete the tasks more efficiently. I usually spend a whole week preparing for it, so I need to complete the tasks more efficiently.

I usually spend a whole week preparing for ita quiz, so this requires me to complete the tasks more efficiently. suggestion: so this time I need to be more efficient. I usually spend a whole week preparing for a quiz, so this requires me to complete the tasks more efficiently. suggestion: so this time I need to be more efficient.

I changed “preparing for it” to “preparing for a quiz,” because “it” makes it sound like you’ve taken this specific quiz before.