Know nothing of the P-99, sorry. I'm surely all thumbs as well. My gunsmith of the time even made me raise my right hand and swear to never disassemble another firearm as I met him at the door with my 700 in one hand and a plastic bag of parts that used to be inside of it in the other.
Still I regularly completely disassemble my Glocks for a really good cleaning every 500-800 rounds. Just follow the above link, if I can do it anybody can.
May just be me but in addition to a really clean gun it builds my confidense in a weapon when I can totally strip it down and put it back together.
Good Luck!