I exchange some coins, after input password and click Exchange Now button , app shows error "Data error when loading from the exchange. Please retry." I click Retry button many times but it does no...

Sorry for the issue that you have experienced. Please be informed that you should not exchange all of balance you have, because exchange transactions need blockchain network fee, and service fee (after 24000 first transactions). Thus, try exchanging with less amount. In addition, In case of XLM, you have to have 1 XLM left after transactions, because Stellar blockchain requires the mimimum amount to remain an account.

For more information, please refer here