You can't make that into one solid quad - either one multi-sided poly or multiple quads, but not both at the same time. Looking at the central highlighted section, select all the polys above the arch (assuming you want that section to have a single material applied to it), with them selected, add a UVWMap Modifier set to Planar. You should then be able to apply a material to the object and have it aligned correctly.
While it might be nice to have regular quads (and in most cases a much better idea) for an object like that it is less important, and careful use of Mapping Modifiers should give you the results you need.
You will need to do some reading on UVW Mapping, Map Channels, Multi SubObject Materials etc in order to fully texture that building.
While it might be nice to have regular quads (and in most cases a much better idea) for an object like that it is less important, and careful use of Mapping Modifiers should give you the results you need.
You will need to do some reading on UVW Mapping, Map Channels, Multi SubObject Materials etc in order to fully texture that building.
It would be possible to eliminate the majority of triangles, but it would take a while to do each one - you would need to consider the cost (in time) vs the benefits (which would be small in this instance).
