Problem with Motorway/Trunk casing.

I am new in OSM(Q-GIS…quantumnik) and I have problems with my Motorway/Trunk casing. I need the casing to be thick… but it seems that lower level roads does not respect casing and “bites in” , see picture. I think, that bridge/tunnel stuff solves only “fill” and not “casing”, I guess nobody expected thick casing. I work with XML. Any advice? Thank you. [Tertiary(white) bites into Motorway(orange casing, yellow fill), while it should go under]