Mortal Online is a large game, and thus it can take a long time to download and install. The good news is that if you've already installed the game patches before, you do not need to download them again.
Browse to your Mortal Online\mortalonline folder and you will find a set of .exe and .mop files. These are the patches your launcher downloaded to install the game. Move or copy these files to another location and then uninstall the game. After reinstalling Mortal Online, copy those files back into the new Mortal Online\mortalonline. After starting the game launcher again it will use those files instead of downloading them all over again.