Hello. I see different platform like nexo, blockifi, etc... that can borrow you crypto or stablecoin. I'm here to ask if you have a strategy for example you borrow btc with an interest rate of 6% and then you use it on defi with 8% APR. Thanks for helpful. 
Borrowing something that has an interest is really risky and it is not really advisable. If we are going to invest in crypto we need to study and see how it works because crypto is an investment that is risky because it is high on volatiliy. No matter how well you plan it, there is always a risk in crypto investment. If you take a loan and unable to make money as planned, you will be in a very difficult situation where you might be in the loss in crypto and then have to pay the loan also. You can earn good too in crypto trading and easily replay the loan but before taking any step, you need to see both side of the picture and be ready for the worse.