How to understand the margin trading in Binance?

I am using Binance. Let’s say I have 0.00102BTC, from which 0.00068BTC. I bought these 0.00068BTC by borrowing Euros. The BTC/EUR ratio is equal to 35,854$. If BTC goes up for 100$ or 0.028BTC then my profit 0.001*0.028 BTC? Maybe there is a way to infer the profit from the ratio given?
Also, I am using cross 3x margin trading, does that “cross 3x” only means that I can borrow 2:1 of what I have?