Hi kdochuk & welcome:
how I can make the files smaller and maintain the quality of the video??
Making files smaller certainly could compromise quality. Much will depend on the amount of compression, the display used to view the files (e.g. SD vs. HD) as well as your standards (what is acceptable to you may not be acceptable to others). Expect about 2 hours of video on a SL DVD.
Burning to DL media will mean you won’t need to compress (but the media is more expensive).
You might look at the settings Dazzle uses and make adjustments on sample clips (experiment).