I use only Shapeshift in the past 2 years and never had any problems, only once I didn't receive my litecoins but it got solved by contacting them. I never tried changelly however I don't blame them but I don't see any reason why I should try another service for instant exchances.
Well be carefully only people that know how to profit make real money, I have a friend which bought almost one bitcoin when the price was almost 15k and now is 9k almost so he lost something. Like I said make more research before you invest, it's kind of lottery this bitcoin thing.
I was in this situation many times... everytime got confirmed sooner or later. Maximum wait time was about 30h+. I know if u hurry to pay/move some coins is very annoying but you have to be patient.