2016 Bmw 340i Check engine/ code p0440

[Froob Loops]

I want to try and diagnose what i need to replace without bringing it into a shop and paying them $100 dollars just to figure out what it is. Ive noticed my idrive efficient dynamics section, showing the mpg i get in the mode i drive has dropped to a solid 10 mpg, even when im just idling. This check engine light came on a day after getting my alignment done.

[Froob Loops]

I just went to fill my tank up at chevron, and it had trouble starting , and the engine light came on, then went away. I went home, and tried to start it again, but it wouldn’t stay running , and threw code p0172