Thanks very much guys for helping me and all these answers!
Just one last question, but I don't know if it's the good place to ask that, I gave a look to the Chuwi HI12, is that a reliable 2 in 1 or it's low quality and I risk it will break or something, I'm willing to use it as offline wallet and offline media player
Have you thought about getting a Trezor (or some other hardware wallet)? Saves a lot of hassle and it's a very secure way to hold and spend bitcoins. Either way, I'd probably recommend Electrum or as a mobile option Mycelium. Those are pretty much the one's that I use and none has failed me yet (except perhaps Electrum with constant syncing problems but I was too lazy to look into it).