Couple Questions about Black Desert Online?

Have since yesterday the game Black Desert Online for the Xbox. Am Level 30 Windrunner and have exactly 2 questions.

1.Question: There are quests that kill 100 creatures. Do I have to kill them individually or is there any equipment for Multikills because the quests last 40 min.

2.Question Buying buildings in the cities, how do you begin as a newbie what building

The housing is a bit complex. Depending on what you want to do you have to rent certain houses. I always found the videos from Refaser very helpful.