It can be discouraging trying to get established selling anything online; dropshipping in particular is even more difficult because its low barrier to entry means anyone at all can give it a go (as you seem to have experienced with 1) below.)
But if I could prod a little for more info:
1)First had many users, who sold same items for much less than me.
You mean people using the same supplier, therefore paying the same price as you for the products? If that's the case, the answer is, very simply, lower your price. What else are you going to do in a case like that?
You should not be doing business with a company if you are not 100% aware of their order and return processes, fees, etc. Setting that aside, if they charge a handling fee per item, chances are you need to find another supplier, or be very selective in which of their products you promote. $5 never seems like much money, until you're trying to turn a profit.
3) the one on Salehoo Stores hasn't brought in any business.
For how long has it been up? What are you doing to promote it?