If you want to reduce the opacity of a single event on the timeline hover the mouse pointer near the top edge of the event and it will turn into a grabby hand with one finger, drag down, a blue line appears across the event showing the opacity level, the farther you drag down the more transparent the clip will become.

You can change the opacity of an entire track by using the level slider in the track header at the left edge of the timeline.

The easiest way to change the speed of a clip is to hold the Ctrl key down while stretching the end of the event to the right to slow it down or squishing to the left to speed it up.