That is impossible to know. The transaction may or may not confirm, it is up to the miners.
let's say that it won't get any confirmations. how long it will take until it will be canceled and everything will come back to normal?
First of all, transactions are not and cannot be canceled. Your wallet can choose to forget about it thus allowing you to respend the inputs, but that does not mean that every other node on the network will do so as well. IIRC blockchain.info will "forget" the transaction after 72 hours unless someone rebroadcasts it.
also, the guy who received who has the full $210 amount, if he will send the amount back to me, will he have any risk to get his wallet on minus?
There is no such thing as a negative balance. If your wallet shows a negative balance, then it has a bug. The Bitcoin does not magically come from another input if the unconfirmed transaction it spends from is invalidated. His wallet will return to being as if it never received the Bitcoin in the first place.
Also, please do not refer to your transactions by any fiat (e.g. USD) amount. The exchange rate constantly changes so it becomes difficult to know what transaction you are talking about. It is better if you give your transactions a label or just refer to it as the first couple characters of the transaction id.