I trade at Bitfinex, I just started margin trading as my initial investment is reduced to 1/4 of initial total.
I borrow money there at 1:3.33 and trade with it.

Question # 1: There must be some interest rate or something like that which I have to pay extra on the borrowed amount but I never knew how much is it. and for how long I can hold that amount, not to incur further loss on paying that interest.

Q # 2: For example I had $100 and I bought 3 LTC with it @ 116$/LTC with leveraged fund. I put sell order @ 120$/LTC and clicked "calculate max. sell". There I was able to sell 5.6 LTC whereas I possessed only 3 LTC. It got me confused.
Furthermore, My sell order executed @ 120$ but it said my position was still open, and when I closed it, it actually executed @ 119$ rate and I got very little profit. I cant understand what happened there. Please help.
Thanking you in anticipation.

I am familiar with a concept of 'time value of money'. In margin trading, If I take that extra amount which exchange offers, it doesn't specifies any time limit for return, which in my view is necessary. What if I hold for 6 months, am I not liable to anything ?
I cant understand this concept in margin trading. Can anyone please guide and help me understand ? Thanks.

I want to invest a big amount for short term, (1-1.5 month). Which alt-coin should I buy to make some profit ? I am really hoping for some sincere suggestions ! Thanks.

Which is the best trading platform for trading in Alt-coins ? There is a problem in Bitfinex, Sometimes the trade gets delayed even hours and that time your money is stuck and you can not trade. If anybody knows solution to this problem, please recommend it. Thanks.

I am using bitfinex for trading of different currencies. When i sell a small currency to buy Bitcoins, there is a delay of 20 mins to 5 hours in execution of that deal. It really bothers me and i am unable to trade during that time. Is there any solution for that problem ? Please help in this regard. Thanking you in anticipation .......