i live in the french speaking part of switzerland. when i came here i knew a bit of french from high school. but over the years i was able to learn the language as well as if not better than many of the locals. french is a complex language and many locals make grammar mistakes in writing although their verbal skills are acceptable. i'm a trainer and i teach communication skills (in french) to the unemployed. cv's cover letters, interview techniques etc. i am often amazed to see the errors made in french by native french speakers.
as for german, i'm not aware about the level of locals in the german speaking area, but......however well you learn "schrifft deutch" you will never master the swiss german dialect, which,sad to say is really baby talk ( i mean no disrespect, but this is the language used by infants and youngsters in primary school ) and now, even carried in to the board room! the good news, is that you can never make spelling mistakes in schwyzerdeutch, because there are no rules, you can write it any way you want. a bit like texting in english