Need Help with computer issues

[Falconius]

Don't know about Sketch Up specifically but my inclination would be that it is a RAM issue. But before going out to get anything, I'd suggest opening up the Windows Task manager then the resource monitor at the bottom of the performance tab and find out specifically what the bottleneck is with a few tests.

In Blender it is possible to have the information in separate files and then call it into the big over file as needed (ie you might make your houses and buildings in various separate files which makes them easy to work on and have an instance in the big file where you are working on the overall shot and you can also use simple block ins or standin blocks until you are ready). The other thing to do is use instances within the same file, which you may already be doing. Instead of copying and pasting a tower you could make one tower and then make instances of the tower which rather than duplicating the information just refers back to the original tower for that information.

Also I don't know how Sketchup handles this sort of thing, but breaking smaller gemoetry down into normal maps or displacement maps where possible as Waldronate suggests would also be very helpful.

Edit: Forgot to mention: that looks really awesome Jo.