Sadly, although there is a resume button, it was disconnected a few upgrades ago. You have to do it manually by killing the download when it stops and restarting it from the original source on the hit list. If that does not work, leave the download in the window and make another search using exactly the same words as the host you are downloading from. That will often reconnect you to the host. If that does not work, it may be because the host has turned his/her machine off so do not despair. Wait a few hours/days and try again. If the computer is switched on again, you will be able to resume the download from the point it stopped.

There is much to learn but it is fun and the rewards are considerable if you master it.

All the best

David