Front ride height and rear spoiler question

[RobGrimsby]

Hi All
sorry for all the questions but having my Boxster S 2004 for just over a week I am still finding out the issues with the car that googleing does answer.
Firstly i seem to be stuggling to get over any speed bumps without scraping the underneeth at the front
I have measured the floor to the top middle of the wheel arch. the height is exctly 24" is this normal. I have 18 inch wheels with low profile tyres.

secondly my spoiler seems to come up as soon as i drive the car and does not retract,
I can manually retarct it with the button inside drivers door, as soon as I drive agin it goes back up, again is this normal

sorrry for all the questions
Thanks
Rob