I want to borrow money from my parents to buy more Bitcoin, because I believe the value is increasing
If 2017 was so exciting about bitcoins prices, you are not wrong if you think that 2018 will be even better than before

... they still doubt it is multi level ponzi, should I invest a lot here or not? I need more advice. Thank all of you a lots...
If they still think that bitcoin is like a mlm ponzi scheme, then they do not know anything about bitcoin, they also do not know anything about mlm ponzi schemes ....
Do not scared your parents, they seems to still need to know a lot about bitcoins, anyway you could invest just a small amount of money so they can feel comfortable with it. In a near future they will be angry with you because you didn't invest more that you did xD