I agree for 2 exchanges mention above but no for GBX exchange honestly never heard of it and look at the volume from coingeko it's too low with no 24hrs volume. For me, it is not safe to use even on the app.

Anyway, Binance is the best option for me to trade Bitcoin "buy and sell" the Binance app is very responsive and never had any issue yet but I am not using it for daily basis I just using it when converting my bitcoin to USDT.
You can find the apps from this URL https://www.binance.com/clientDownloads.html

For KuCoin they are also great I use it to exchange some coins but I mostly trade in Binance.
The right URL to download the KuCoin app you can find from here https://www.kucoin.com/download