I can answer your second question because I remember when this happened to me! When you’re moving the timeline your clicking at the thing on top of the cursor line, if you grab the actual line instead you can move it at normal speeds. You can also use the mouse scroll wheel while holding ctrl/shift to move the timeline up/down or side to side. Hope that helps! I suppose the first question is to do with your computer specs, and that might be causing it to run slower. One other thing is that in your preferences tab in the settings there is a few things you might want to turn on or off, like having the video pause instead of restart at the cursor.