Fat

see http://www.fatismyfriend.co.uk/ and https://www.atkins.com/how-it-works/library/articles/good-fats and https://ketodietapp.com/Blog/post/2014/01/29/Complete-Guide-to-Fats-Oils-on-Low-Carb-Ketogenic-Diet

Natural animal fats are good, industrially processed plant oils are bad.

When you lower the quantity of carbs in your diet then you have to replace the energy you get from those carbs with energy from fats. The cholesterol level question is controversial and many people are worried about it so it must be your personal choice as to whether you get your fats from olives, olive oil, avocado, nuts etc or you get your fats from animal fats and dairy products. My personal choice is to get my main source of fat from animal products and I do not worry about my cholesterol but I have done my research and I have made my own choices. Good luck.

There's been quite a lot of recent research amd also meta-analysis of research that suggests that consumption of fats does not have an adverse affect on cholesterol levels and morbidity.