Madak,

Yes you can. Audio objects have three little icons on a line in their track (middle is diamond shape and ends are five sided). Drag the middle one up/down to overall change volume or drag the ends ones down for fade-in and fade-out.

For volume changes within a clip see my reply about using the track volume curve here:

http://www.magix.info/us/i-would-like-to-edit-the-sound-track-of.knowledge.375160.html

Regards,

Carl