New beginner questions for timeline window

There is a white spot near the time duration, when I accidentally move it to the right the left side of the playhead timeline background turn light grey and the right side is dark, what does it do?
Second question is every time I start DaVinci 15 the text effect need to rendering again, is it normal?
Last question is when I use F9 to insert clip, it doesn’t fit into the play head, it insert somewhere far behind position, how to correct this?
Thanks
Second question is every time I start DaVinci 15 the text effect need to rendering again, is it normal?
Last question is when I use F9 to insert clip, it doesn’t fit into the play head, it insert somewhere far behind position, how to correct this?
Thanks