How to video reduce size

[veravin]

Please, how to i reduce my video size, but keep quality, i av tried handbreak, but it keeps increasing the size, i cant download an older version any where and most of my files are flv, so i cannot use imovie to reduce their size.

Please how do i reduce the size and keep quality, an app, anything would be use, please explain, so its easier to understand.

THANKS