If it's dropped from the network how do you the get BTC back in your wallet?
It is as if it never left the wallet. If a transaction is dropped, it is as if the transaction never existed so the Bitcoin remains as if the transaction never happened.
What is the best fee amount when we send bitcoins from one wallet to another one.
I really hate now transactions, when i see people waiting for days.
I haven't sent transactions during this time, so I can't really say. But if I do send transactions, it will be double what Bitcoin Core defaults to recommending e.g. 0.0002 per Kb instead of 0.0001 per Kb.