Safety of BTC wallet is the most important 
Especially online BTC wallets - as we all know. And also well developed hardware wallet safety and fast transaction times 
Exactly! Safety first. Maybe one of the problem is that, the payment is quiet late but that's normal Especially online BTC wallets - as we all know. And also well developed hardware wallet safety and fast transaction times But i trust it, so no reason to have a problem in bitcoin. there is a lot of problem to be complained about how bitcoin have a disadvantages ,
like when you are send money to a wrong address you can cancel it ,
also the offline store seems not ready yet accept bitcoin and many more.
Cancelling it wont be possible that is true. But regarding the retail physical stores it can be managed when time comes. Just need a some adaption from different owners. Some does this already and somehow it works for them.
how if one of between buyer and seller have a bad intention ,
and they just won't do the refund / cancel ?
the bitcoin feature like this have more disadvantages instead an advantage imo.